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</pre><pre class="rust ">
<span class="comment">// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT</span>
<span class="comment">// file at the top-level directory of this distribution and at</span>
<span class="comment">// http://rust-lang.org/COPYRIGHT.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="doccomment">//! Optional values.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Type [`Option`] represents an optional value: every [`Option`]</span>
<span class="doccomment">//! is either [`Some`] and contains a value, or [`None`], and</span>
<span class="doccomment">//! does not. [`Option`] types are very common in Rust code, as</span>
<span class="doccomment">//! they have a number of uses:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! * Initial values</span>
<span class="doccomment">//! * Return values for functions that are not defined</span>
<span class="doccomment">//! over their entire input range (partial functions)</span>
<span class="doccomment">//! * Return value for otherwise reporting simple errors, where `None` is</span>
<span class="doccomment">//! returned on error</span>
<span class="doccomment">//! * Optional struct fields</span>
<span class="doccomment">//! * Struct fields that can be loaned or "taken"</span>
<span class="doccomment">//! * Optional function arguments</span>
<span class="doccomment">//! * Nullable pointers</span>
<span class="doccomment">//! * Swapping things out of difficult situations</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! [`Option`]s are commonly paired with pattern matching to query the presence</span>
<span class="doccomment">//! of a value and take action, always accounting for the [`None`] case.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! fn divide(numerator: f64, denominator: f64) -> Option<f64> {</span>
<span class="doccomment">//! if denominator == 0.0 {</span>
<span class="doccomment">//! None</span>
<span class="doccomment">//! } else {</span>
<span class="doccomment">//! Some(numerator / denominator)</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // The return value of the function is an option</span>
<span class="doccomment">//! let result = divide(2.0, 3.0);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Pattern match to retrieve the value</span>
<span class="doccomment">//! match result {</span>
<span class="doccomment">//! // The division was valid</span>
<span class="doccomment">//! Some(x) => println!("Result: {}", x),</span>
<span class="doccomment">//! // The division was invalid</span>
<span class="doccomment">//! None => println!("Cannot divide by 0"),</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="comment">//</span>
<span class="comment">// FIXME: Show how `Option` is used in practice, with lots of methods</span>
<span class="comment">//</span>
<span class="doccomment">//! # Options and pointers ("nullable" pointers)</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Rust's pointer types must always point to a valid location; there are</span>
<span class="doccomment">//! no "null" pointers. Instead, Rust has *optional* pointers, like</span>
<span class="doccomment">//! the optional owned box, [`Option`]`<`[`Box<T>`]`>`.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! The following example uses [`Option`] to create an optional box of</span>
<span class="doccomment">//! [`i32`]. Notice that in order to use the inner [`i32`] value first, the</span>
<span class="doccomment">//! `check_optional` function needs to use pattern matching to</span>
<span class="doccomment">//! determine whether the box has a value (i.e. it is [`Some(...)`][`Some`]) or</span>
<span class="doccomment">//! not ([`None`]).</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! let optional = None;</span>
<span class="doccomment">//! check_optional(optional);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let optional = Some(Box::new(9000));</span>
<span class="doccomment">//! check_optional(optional);</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! fn check_optional(optional: Option<Box<i32>>) {</span>
<span class="doccomment">//! match optional {</span>
<span class="doccomment">//! Some(ref p) => println!("has value {}", p),</span>
<span class="doccomment">//! None => println!("has no value"),</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! This usage of [`Option`] to create safe nullable pointers is so</span>
<span class="doccomment">//! common that Rust does special optimizations to make the</span>
<span class="doccomment">//! representation of [`Option`]`<`[`Box<T>`]`>` a single pointer. Optional pointers</span>
<span class="doccomment">//! in Rust are stored as efficiently as any other pointer type.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Examples</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Basic pattern matching on [`Option`]:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! let msg = Some("howdy");</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Take a reference to the contained string</span>
<span class="doccomment">//! if let Some(ref m) = msg {</span>
<span class="doccomment">//! println!("{}", *m);</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Remove the contained string, destroying the Option</span>
<span class="doccomment">//! let unwrapped_msg = msg.unwrap_or("default message");</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Initialize a result to [`None`] before a loop:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! enum Kingdom { Plant(u32, &'static str), Animal(u32, &'static str) }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // A list of data to search through.</span>
<span class="doccomment">//! let all_the_big_things = [</span>
<span class="doccomment">//! Kingdom::Plant(250, "redwood"),</span>
<span class="doccomment">//! Kingdom::Plant(230, "noble fir"),</span>
<span class="doccomment">//! Kingdom::Plant(229, "sugar pine"),</span>
<span class="doccomment">//! Kingdom::Animal(25, "blue whale"),</span>
<span class="doccomment">//! Kingdom::Animal(19, "fin whale"),</span>
<span class="doccomment">//! Kingdom::Animal(15, "north pacific right whale"),</span>
<span class="doccomment">//! ];</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // We're going to search for the name of the biggest animal,</span>
<span class="doccomment">//! // but to start with we've just got `None`.</span>
<span class="doccomment">//! let mut name_of_biggest_animal = None;</span>
<span class="doccomment">//! let mut size_of_biggest_animal = 0;</span>
<span class="doccomment">//! for big_thing in &all_the_big_things {</span>
<span class="doccomment">//! match *big_thing {</span>
<span class="doccomment">//! Kingdom::Animal(size, name) if size > size_of_biggest_animal => {</span>
<span class="doccomment">//! // Now we've found the name of some big animal</span>
<span class="doccomment">//! size_of_biggest_animal = size;</span>
<span class="doccomment">//! name_of_biggest_animal = Some(name);</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! Kingdom::Animal(..) | Kingdom::Plant(..) => ()</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! match name_of_biggest_animal {</span>
<span class="doccomment">//! Some(name) => println!("the biggest animal is {}", name),</span>
<span class="doccomment">//! None => println!("there are no animals :("),</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! [`Option`]: enum.Option.html</span>
<span class="doccomment">//! [`Some`]: enum.Option.html#variant.Some</span>
<span class="doccomment">//! [`None`]: enum.Option.html#variant.None</span>
<span class="doccomment">//! [`Box<T>`]: ../../std/boxed/struct.Box.html</span>
<span class="doccomment">//! [`i32`]: ../../std/primitive.i32.html</span>
<span class="attribute">#<span class="op">!</span>[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">use</span> <span class="ident">iter</span>::{<span class="ident">FromIterator</span>, <span class="ident">FusedIterator</span>, <span class="ident">TrustedLen</span>};
<span class="kw">use</span> <span class="ident">mem</span>;
<span class="comment">// Note that this is not a lang item per se, but it has a hidden dependency on</span>
<span class="comment">// `Iterator`, which is one. The compiler assumes that the `next` method of</span>
<span class="comment">// `Iterator` is an enumeration with one type parameter and two variants,</span>
<span class="comment">// which basically means it must be `Option`.</span>
<span class="doccomment">/// The `Option` type. See [the module level documentation](index.html) for more.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">PartialEq</span>, <span class="ident">PartialOrd</span>, <span class="ident">Eq</span>, <span class="ident">Ord</span>, <span class="ident">Debug</span>, <span class="ident">Hash</span>)]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// No value</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="prelude-val">None</span>,
<span class="doccomment">/// Some value `T`</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="prelude-val">Some</span>(<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span> <span class="ident">T</span>),
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Type implementation</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Querying the contained values</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Returns `true` if the option is a [`Some`] value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Option<u32> = Some(2);</span>
<span class="doccomment">/// assert_eq!(x.is_some(), true);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Option<u32> = None;</span>
<span class="doccomment">/// assert_eq!(x.is_some(), false);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Some`]: #variant.Some</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">is_some</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="prelude-val">Some</span>(_) <span class="op">=></span> <span class="bool-val">true</span>,
<span class="prelude-val">None</span> <span class="op">=></span> <span class="bool-val">false</span>,
}
}
<span class="doccomment">/// Returns `true` if the option is a [`None`] value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x: Option<u32> = Some(2);</span>
<span class="doccomment">/// assert_eq!(x.is_none(), false);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Option<u32> = None;</span>
<span class="doccomment">/// assert_eq!(x.is_none(), true);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">is_none</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="op">!</span><span class="self">self</span>.<span class="ident">is_some</span>()
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Adapter for working with references</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Converts from `Option<T>` to `Option<&T>`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Convert an `Option<`[`String`]`>` into an `Option<`[`usize`]`>`, preserving the original.</span>
<span class="doccomment">/// The [`map`] method takes the `self` argument by value, consuming the original,</span>
<span class="doccomment">/// so this technique uses `as_ref` to first take an `Option` to a reference</span>
<span class="doccomment">/// to the value inside the original.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`map`]: enum.Option.html#method.map</span>
<span class="doccomment">/// [`String`]: ../../std/string/struct.String.html</span>
<span class="doccomment">/// [`usize`]: ../../std/primitive.usize.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let num_as_str: Option<String> = Some("10".to_string());</span>
<span class="doccomment">/// // First, cast `Option<String>` to `Option<&String>` with `as_ref`,</span>
<span class="doccomment">/// // then consume *that* with `map`, leaving `num_as_str` on the stack.</span>
<span class="doccomment">/// let num_as_int: Option<usize> = num_as_str.as_ref().map(|n| n.len());</span>
<span class="doccomment">/// println!("still can print num_as_str: {:?}", num_as_str);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">as_ref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="kw-2">ref</span> <span class="ident">x</span>) <span class="op">=></span> <span class="prelude-val">Some</span>(<span class="ident">x</span>),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
<span class="doccomment">/// Converts from `Option<T>` to `Option<&mut T>`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let mut x = Some(2);</span>
<span class="doccomment">/// match x.as_mut() {</span>
<span class="doccomment">/// Some(v) => *v = 42,</span>
<span class="doccomment">/// None => {},</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// assert_eq!(x, Some(42));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">as_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span><span class="op">></span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">x</span>) <span class="op">=></span> <span class="prelude-val">Some</span>(<span class="ident">x</span>),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Getting to contained values</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Unwraps an option, yielding the content of a [`Some`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if the value is a [`None`] with a custom panic message provided by</span>
<span class="doccomment">/// `msg`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Some`]: #variant.Some</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x = Some("value");</span>
<span class="doccomment">/// assert_eq!(x.expect("the world is ending"), "value");</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```{.should_panic}</span>
<span class="doccomment">/// let x: Option<&str> = None;</span>
<span class="doccomment">/// x.expect("the world is ending"); // panics with `the world is ending`</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">expect</span>(<span class="self">self</span>, <span class="ident">msg</span>: <span class="kw-2">&</span><span class="ident">str</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">val</span>) <span class="op">=></span> <span class="ident">val</span>,
<span class="prelude-val">None</span> <span class="op">=></span> <span class="ident">expect_failed</span>(<span class="ident">msg</span>),
}
}
<span class="doccomment">/// Moves the value `v` out of the `Option<T>` if it is [`Some(v)`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// In general, because this function may panic, its use is discouraged.</span>
<span class="doccomment">/// Instead, prefer to use pattern matching and handle the [`None`]</span>
<span class="doccomment">/// case explicitly.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if the self value equals [`None`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Some(v)`]: #variant.Some</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x = Some("air");</span>
<span class="doccomment">/// assert_eq!(x.unwrap(), "air");</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```{.should_panic}</span>
<span class="doccomment">/// let x: Option<&str> = None;</span>
<span class="doccomment">/// assert_eq!(x.unwrap(), "air"); // fails</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">unwrap</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">val</span>) <span class="op">=></span> <span class="ident">val</span>,
<span class="prelude-val">None</span> <span class="op">=></span> <span class="macro">panic</span><span class="macro">!</span>(<span class="string">"called `Option::unwrap()` on a `None` value"</span>),
}
}
<span class="doccomment">/// Returns the contained value or a default.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// assert_eq!(Some("car").unwrap_or("bike"), "car");</span>
<span class="doccomment">/// assert_eq!(None.unwrap_or("bike"), "bike");</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">unwrap_or</span>(<span class="self">self</span>, <span class="ident">def</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">x</span>) <span class="op">=></span> <span class="ident">x</span>,
<span class="prelude-val">None</span> <span class="op">=></span> <span class="ident">def</span>,
}
}
<span class="doccomment">/// Returns the contained value or computes it from a closure.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let k = 10;</span>
<span class="doccomment">/// assert_eq!(Some(4).unwrap_or_else(|| 2 * k), 4);</span>
<span class="doccomment">/// assert_eq!(None.unwrap_or_else(|| 2 * k), 20);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">unwrap_or_else</span><span class="op"><</span><span class="ident">F</span>: <span class="ident">FnOnce</span>() <span class="op">-></span> <span class="ident">T</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">x</span>) <span class="op">=></span> <span class="ident">x</span>,
<span class="prelude-val">None</span> <span class="op">=></span> <span class="ident">f</span>(),
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Transforming contained values</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Maps an `Option<T>` to `Option<U>` by applying a function to a contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Convert an `Option<`[`String`]`>` into an `Option<`[`usize`]`>`, consuming the original:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`String`]: ../../std/string/struct.String.html</span>
<span class="doccomment">/// [`usize`]: ../../std/primitive.usize.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let maybe_some_string = Some(String::from("Hello, World!"));</span>
<span class="doccomment">/// // `Option::map` takes self *by value*, consuming `maybe_some_string`</span>
<span class="doccomment">/// let maybe_some_len = maybe_some_string.map(|s| s.len());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(maybe_some_len, Some(13));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">map</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="ident">T</span>) <span class="op">-></span> <span class="ident">U</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">x</span>) <span class="op">=></span> <span class="prelude-val">Some</span>(<span class="ident">f</span>(<span class="ident">x</span>)),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
<span class="doccomment">/// Applies a function to the contained value (if any),</span>
<span class="doccomment">/// or returns a [`default`][] (if not).</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`default`]: ../default/trait.Default.html#tymethod.default</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x = Some("foo");</span>
<span class="doccomment">/// assert_eq!(x.map_or(42, |v| v.len()), 3);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Option<&str> = None;</span>
<span class="doccomment">/// assert_eq!(x.map_or(42, |v| v.len()), 42);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">map_or</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="ident">T</span>) <span class="op">-></span> <span class="ident">U</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">default</span>: <span class="ident">U</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">U</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="ident">f</span>(<span class="ident">t</span>),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="ident">default</span>,
}
}
<span class="doccomment">/// Applies a function to the contained value (if any),</span>
<span class="doccomment">/// or computes a [`default`][] (if not).</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`default`]: ../default/trait.Default.html#tymethod.default</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let k = 21;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = Some("foo");</span>
<span class="doccomment">/// assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 3);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Option<&str> = None;</span>
<span class="doccomment">/// assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 42);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">map_or_else</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">D</span>: <span class="ident">FnOnce</span>() <span class="op">-></span> <span class="ident">U</span>, <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="ident">T</span>) <span class="op">-></span> <span class="ident">U</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">default</span>: <span class="ident">D</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">U</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">t</span>) <span class="op">=></span> <span class="ident">f</span>(<span class="ident">t</span>),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="ident">default</span>(),
}
}
<span class="doccomment">/// Transforms the `Option<T>` into a [`Result<T, E>`], mapping [`Some(v)`] to</span>
<span class="doccomment">/// [`Ok(v)`] and [`None`] to [`Err(err)`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Result<T, E>`]: ../../std/result/enum.Result.html</span>
<span class="doccomment">/// [`Ok(v)`]: ../../std/result/enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err(err)`]: ../../std/result/enum.Result.html#variant.Err</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="doccomment">/// [`Some(v)`]: #variant.Some</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x = Some("foo");</span>
<span class="doccomment">/// assert_eq!(x.ok_or(0), Ok("foo"));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Option<&str> = None;</span>
<span class="doccomment">/// assert_eq!(x.ok_or(0), Err(0));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">ok_or</span><span class="op"><</span><span class="ident">E</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">err</span>: <span class="ident">E</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">v</span>) <span class="op">=></span> <span class="prelude-val">Ok</span>(<span class="ident">v</span>),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="ident">err</span>),
}
}
<span class="doccomment">/// Transforms the `Option<T>` into a [`Result<T, E>`], mapping [`Some(v)`] to</span>
<span class="doccomment">/// [`Ok(v)`] and [`None`] to [`Err(err())`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Result<T, E>`]: ../../std/result/enum.Result.html</span>
<span class="doccomment">/// [`Ok(v)`]: ../../std/result/enum.Result.html#variant.Ok</span>
<span class="doccomment">/// [`Err(err())`]: ../../std/result/enum.Result.html#variant.Err</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="doccomment">/// [`Some(v)`]: #variant.Some</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x = Some("foo");</span>
<span class="doccomment">/// assert_eq!(x.ok_or_else(|| 0), Ok("foo"));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Option<&str> = None;</span>
<span class="doccomment">/// assert_eq!(x.ok_or_else(|| 0), Err(0));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">ok_or_else</span><span class="op"><</span><span class="ident">E</span>, <span class="ident">F</span>: <span class="ident">FnOnce</span>() <span class="op">-></span> <span class="ident">E</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">err</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">E</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">v</span>) <span class="op">=></span> <span class="prelude-val">Ok</span>(<span class="ident">v</span>),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="ident">err</span>()),
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Iterator constructors</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Returns an iterator over the possibly contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x = Some(4);</span>
<span class="doccomment">/// assert_eq!(x.iter().next(), Some(&4));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Option<u32> = None;</span>
<span class="doccomment">/// assert_eq!(x.iter().next(), None);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">iter</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Iter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">Iter</span> { <span class="ident">inner</span>: <span class="ident">Item</span> { <span class="ident">opt</span>: <span class="self">self</span>.<span class="ident">as_ref</span>() } }
}
<span class="doccomment">/// Returns a mutable iterator over the possibly contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let mut x = Some(4);</span>
<span class="doccomment">/// match x.iter_mut().next() {</span>
<span class="doccomment">/// Some(v) => *v = 42,</span>
<span class="doccomment">/// None => {},</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// assert_eq!(x, Some(42));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut x: Option<u32> = None;</span>
<span class="doccomment">/// assert_eq!(x.iter_mut().next(), None);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">iter_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">IterMut</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">IterMut</span> { <span class="ident">inner</span>: <span class="ident">Item</span> { <span class="ident">opt</span>: <span class="self">self</span>.<span class="ident">as_mut</span>() } }
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Boolean operations on the values, eager and lazy</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Returns [`None`] if the option is [`None`], otherwise returns `optb`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x = Some(2);</span>
<span class="doccomment">/// let y: Option<&str> = None;</span>
<span class="doccomment">/// assert_eq!(x.and(y), None);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Option<u32> = None;</span>
<span class="doccomment">/// let y = Some("foo");</span>
<span class="doccomment">/// assert_eq!(x.and(y), None);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = Some(2);</span>
<span class="doccomment">/// let y = Some("foo");</span>
<span class="doccomment">/// assert_eq!(x.and(y), Some("foo"));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Option<u32> = None;</span>
<span class="doccomment">/// let y: Option<&str> = None;</span>
<span class="doccomment">/// assert_eq!(x.and(y), None);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">and</span><span class="op"><</span><span class="ident">U</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">optb</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">U</span><span class="op">></span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(_) <span class="op">=></span> <span class="ident">optb</span>,
<span class="prelude-val">None</span> <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
<span class="doccomment">/// Returns [`None`] if the option is [`None`], otherwise calls `f` with the</span>
<span class="doccomment">/// wrapped value and returns the result.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Some languages call this operation flatmap.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// fn sq(x: u32) -> Option<u32> { Some(x * x) }</span>
<span class="doccomment">/// fn nope(_: u32) -> Option<u32> { None }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(Some(2).and_then(sq).and_then(sq), Some(16));</span>
<span class="doccomment">/// assert_eq!(Some(2).and_then(sq).and_then(nope), None);</span>
<span class="doccomment">/// assert_eq!(Some(2).and_then(nope).and_then(sq), None);</span>
<span class="doccomment">/// assert_eq!(None.and_then(sq).and_then(sq), None);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">and_then</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="ident">T</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">U</span><span class="op">>></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">x</span>) <span class="op">=></span> <span class="ident">f</span>(<span class="ident">x</span>),
<span class="prelude-val">None</span> <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
<span class="doccomment">/// Returns the option if it contains a value, otherwise returns `optb`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x = Some(2);</span>
<span class="doccomment">/// let y = None;</span>
<span class="doccomment">/// assert_eq!(x.or(y), Some(2));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = None;</span>
<span class="doccomment">/// let y = Some(100);</span>
<span class="doccomment">/// assert_eq!(x.or(y), Some(100));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = Some(2);</span>
<span class="doccomment">/// let y = Some(100);</span>
<span class="doccomment">/// assert_eq!(x.or(y), Some(2));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Option<u32> = None;</span>
<span class="doccomment">/// let y = None;</span>
<span class="doccomment">/// assert_eq!(x.or(y), None);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">or</span>(<span class="self">self</span>, <span class="ident">optb</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(_) <span class="op">=></span> <span class="self">self</span>,
<span class="prelude-val">None</span> <span class="op">=></span> <span class="ident">optb</span>,
}
}
<span class="doccomment">/// Returns the option if it contains a value, otherwise calls `f` and</span>
<span class="doccomment">/// returns the result.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// fn nobody() -> Option<&'static str> { None }</span>
<span class="doccomment">/// fn vikings() -> Option<&'static str> { Some("vikings") }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(Some("barbarians").or_else(vikings), Some("barbarians"));</span>
<span class="doccomment">/// assert_eq!(None.or_else(vikings), Some("vikings"));</span>
<span class="doccomment">/// assert_eq!(None.or_else(nobody), None);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">or_else</span><span class="op"><</span><span class="ident">F</span>: <span class="ident">FnOnce</span>() <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(_) <span class="op">=></span> <span class="self">self</span>,
<span class="prelude-val">None</span> <span class="op">=></span> <span class="ident">f</span>(),
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Entry-like operations to insert if None and return a reference</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Inserts `v` into the option if it is [`None`], then</span>
<span class="doccomment">/// returns a mutable reference to the contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// #![feature(option_entry)]</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut x = None;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// {</span>
<span class="doccomment">/// let y: &mut u32 = x.get_or_insert(5);</span>
<span class="doccomment">/// assert_eq!(y, &5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// *y = 7;</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(x, Some(7));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"option_entry"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"39288"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_or_insert</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">v</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="prelude-val">None</span> <span class="op">=></span> <span class="kw-2">*</span><span class="self">self</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">v</span>),
_ <span class="op">=></span> (),
}
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">v</span>) <span class="op">=></span> <span class="ident">v</span>,
_ <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
}
}
<span class="doccomment">/// Inserts a value computed from `f` into the option if it is [`None`], then</span>
<span class="doccomment">/// returns a mutable reference to the contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// #![feature(option_entry)]</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut x = None;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// {</span>
<span class="doccomment">/// let y: &mut u32 = x.get_or_insert_with(|| 5);</span>
<span class="doccomment">/// assert_eq!(y, &5);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// *y = 7;</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(x, Some(7));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"option_entry"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"39288"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_or_insert_with</span><span class="op"><</span><span class="ident">F</span>: <span class="ident">FnOnce</span>() <span class="op">-></span> <span class="ident">T</span><span class="op">></span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="prelude-val">None</span> <span class="op">=></span> <span class="kw-2">*</span><span class="self">self</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">f</span>()),
_ <span class="op">=></span> (),
}
<span class="kw">match</span> <span class="kw-2">*</span><span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="kw-2">ref</span> <span class="kw-2">mut</span> <span class="ident">v</span>) <span class="op">=></span> <span class="ident">v</span>,
_ <span class="op">=></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Misc</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////</span>
<span class="doccomment">/// Takes the value out of the option, leaving a [`None`] in its place.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let mut x = Some(2);</span>
<span class="doccomment">/// x.take();</span>
<span class="doccomment">/// assert_eq!(x, None);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut x: Option<u32> = None;</span>
<span class="doccomment">/// x.take();</span>
<span class="doccomment">/// assert_eq!(x, None);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">take</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">mem</span>::<span class="ident">replace</span>(<span class="self">self</span>, <span class="prelude-val">None</span>)
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="ident">Clone</span><span class="op">></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Maps an `Option<&T>` to an `Option<T>` by cloning the contents of the</span>
<span class="doccomment">/// option.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x = 12;</span>
<span class="doccomment">/// let opt_x = Some(&x);</span>
<span class="doccomment">/// assert_eq!(opt_x, Some(&12));</span>
<span class="doccomment">/// let cloned = opt_x.cloned();</span>
<span class="doccomment">/// assert_eq!(cloned, Some(12));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">cloned</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">map</span>(<span class="op">|</span><span class="ident">t</span><span class="op">|</span> <span class="ident">t</span>.<span class="ident">clone</span>())
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Default</span><span class="op">></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Returns the contained value or a default</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Consumes the `self` argument then, if [`Some`], returns the contained</span>
<span class="doccomment">/// value, otherwise if [`None`], returns the default value for that</span>
<span class="doccomment">/// type.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Convert a string to an integer, turning poorly-formed strings</span>
<span class="doccomment">/// into 0 (the default value for integers). [`parse`] converts</span>
<span class="doccomment">/// a string to any other type that implements [`FromStr`], returning</span>
<span class="doccomment">/// [`None`] on error.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let good_year_from_input = "1909";</span>
<span class="doccomment">/// let bad_year_from_input = "190blarg";</span>
<span class="doccomment">/// let good_year = good_year_from_input.parse().ok().unwrap_or_default();</span>
<span class="doccomment">/// let bad_year = bad_year_from_input.parse().ok().unwrap_or_default();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(1909, good_year);</span>
<span class="doccomment">/// assert_eq!(0, bad_year);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Some`]: #variant.Some</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="doccomment">/// [`parse`]: ../../std/primitive.str.html#method.parse</span>
<span class="doccomment">/// [`FromStr`]: ../../std/str/trait.FromStr.html</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">unwrap_or_default</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">match</span> <span class="self">self</span> {
<span class="prelude-val">Some</span>(<span class="ident">x</span>) <span class="op">=></span> <span class="ident">x</span>,
<span class="prelude-val">None</span> <span class="op">=></span> <span class="ident">Default</span>::<span class="ident">default</span>(),
}
}
}
<span class="comment">// This is a separate function to reduce the code size of .expect() itself.</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">never</span>)]</span>
<span class="attribute">#[<span class="ident">cold</span>]</span>
<span class="kw">fn</span> <span class="ident">expect_failed</span>(<span class="ident">msg</span>: <span class="kw-2">&</span><span class="ident">str</span>) <span class="op">-></span> <span class="op">!</span> {
<span class="macro">panic</span><span class="macro">!</span>(<span class="string">"{}"</span>, <span class="ident">msg</span>)
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// Trait implementations</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Default</span> <span class="kw">for</span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Returns [`None`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`None`]: #variant.None</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="prelude-val">None</span> }
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">IntoIterator</span> <span class="kw">for</span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="kw">type</span> <span class="ident">IntoIter</span> <span class="op">=</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>;
<span class="doccomment">/// Returns a consuming iterator over the possibly contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let x = Some("string");</span>
<span class="doccomment">/// let v: Vec<&str> = x.into_iter().collect();</span>
<span class="doccomment">/// assert_eq!(v, ["string"]);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = None;</span>
<span class="doccomment">/// let v: Vec<&str> = x.into_iter().collect();</span>
<span class="doccomment">/// assert!(v.is_empty());</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">into_iter</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">IntoIter</span> { <span class="ident">inner</span>: <span class="ident">Item</span> { <span class="ident">opt</span>: <span class="self">self</span> } }
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"option_iter"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">IntoIterator</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">T</span>;
<span class="kw">type</span> <span class="ident">IntoIter</span> <span class="op">=</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>;
<span class="kw">fn</span> <span class="ident">into_iter</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">iter</span>()
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"1.4.0"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"option_iter"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">IntoIterator</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span>;
<span class="kw">type</span> <span class="ident">IntoIter</span> <span class="op">=</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>;
<span class="kw">fn</span> <span class="ident">into_iter</span>(<span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">iter_mut</span>()
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">since</span> <span class="op">=</span> <span class="string">"1.12.0"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"option_from"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">From</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">val</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="prelude-val">Some</span>(<span class="ident">val</span>)
}
}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// The Option Iterators</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">struct</span> <span class="ident">Item</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {
<span class="ident">opt</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">A</span><span class="op">></span>
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">Iterator</span> <span class="kw">for</span> <span class="ident">Item</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">A</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">opt</span>.<span class="ident">take</span>()
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">size_hint</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> (<span class="ident">usize</span>, <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>) {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">opt</span> {
<span class="prelude-val">Some</span>(_) <span class="op">=></span> (<span class="number">1</span>, <span class="prelude-val">Some</span>(<span class="number">1</span>)),
<span class="prelude-val">None</span> <span class="op">=></span> (<span class="number">0</span>, <span class="prelude-val">Some</span>(<span class="number">0</span>)),
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">DoubleEndedIterator</span> <span class="kw">for</span> <span class="ident">Item</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">opt</span>.<span class="ident">take</span>()
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">ExactSizeIterator</span> <span class="kw">for</span> <span class="ident">Item</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {}
<span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">FusedIterator</span> <span class="kw">for</span> <span class="ident">Item</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">TrustedLen</span> <span class="kw">for</span> <span class="ident">Item</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {}
<span class="doccomment">/// An iterator over a reference to the [`Some`] variant of an [`Option`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This `struct` is created by the [`Option::iter`] function.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Option`]: enum.Option.html</span>
<span class="doccomment">/// [`Some`]: enum.Option.html#variant.Some</span>
<span class="doccomment">/// [`Option::iter`]: enum.Option.html#method.iter</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span>: <span class="lifetime">'a</span><span class="op">></span> { <span class="ident">inner</span>: <span class="ident">Item</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">A</span><span class="op">></span> }
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">Iterator</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">A</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">A</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">next</span>() }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">size_hint</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> (<span class="ident">usize</span>, <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>) { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">size_hint</span>() }
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">DoubleEndedIterator</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">A</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">next_back</span>() }
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">ExactSizeIterator</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"fused"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"35602"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">FusedIterator</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"trusted_len"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"37572"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">TrustedLen</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">Clone</span> <span class="kw">for</span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">clone</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">Iter</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {
<span class="ident">Iter</span> { <span class="ident">inner</span>: <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">clone</span>() }
}
}
<span class="doccomment">/// An iterator over a mutable reference to the [`Some`] variant of an [`Option`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This `struct` is created by the [`Option::iter_mut`] function.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Option`]: enum.Option.html</span>
<span class="doccomment">/// [`Some`]: enum.Option.html#variant.Some</span>
<span class="doccomment">/// [`Option::iter_mut`]: enum.Option.html#method.iter_mut</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span>: <span class="lifetime">'a</span><span class="op">></span> { <span class="ident">inner</span>: <span class="ident">Item</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">A</span><span class="op">></span> }
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">Iterator</span> <span class="kw">for</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">A</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">A</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">next</span>() }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">size_hint</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> (<span class="ident">usize</span>, <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>) { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">size_hint</span>() }
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">DoubleEndedIterator</span> <span class="kw">for</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">A</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">next_back</span>() }
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">ExactSizeIterator</span> <span class="kw">for</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"fused"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"35602"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">FusedIterator</span> <span class="kw">for</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"trusted_len"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"37572"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> <span class="ident">TrustedLen</span> <span class="kw">for</span> <span class="ident">IterMut</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span><span class="op">></span> {}
<span class="doccomment">/// An iterator over the value in [`Some`] variant of an [`Option`].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This `struct` is created by the [`Option::into_iter`] function.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Option`]: enum.Option.html</span>
<span class="doccomment">/// [`Some`]: enum.Option.html#variant.Some</span>
<span class="doccomment">/// [`Option::into_iter`]: enum.Option.html#method.into_iter</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> { <span class="ident">inner</span>: <span class="ident">Item</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> }
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">Iterator</span> <span class="kw">for</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">A</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">next</span>() }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">size_hint</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> (<span class="ident">usize</span>, <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">usize</span><span class="op">></span>) { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">size_hint</span>() }
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">DoubleEndedIterator</span> <span class="kw">for</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next_back</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> { <span class="self">self</span>.<span class="ident">inner</span>.<span class="ident">next_back</span>() }
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">ExactSizeIterator</span> <span class="kw">for</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"fused"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"35602"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">FusedIterator</span> <span class="kw">for</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"trusted_len"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"37572"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> <span class="ident">TrustedLen</span> <span class="kw">for</span> <span class="ident">IntoIter</span><span class="op"><</span><span class="ident">A</span><span class="op">></span> {}
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="comment">// FromIterator</span>
<span class="comment">/////////////////////////////////////////////////////////////////////////////</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">A</span>, <span class="ident">V</span>: <span class="ident">FromIterator</span><span class="op"><</span><span class="ident">A</span><span class="op">>></span> <span class="ident">FromIterator</span><span class="op"><</span><span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">A</span><span class="op">>></span> <span class="kw">for</span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">V</span><span class="op">></span> {
<span class="doccomment">/// Takes each element in the [`Iterator`]: if it is [`None`], no further</span>
<span class="doccomment">/// elements are taken, and the [`None`] is returned. Should no [`None`] occur, a</span>
<span class="doccomment">/// container with the values of each `Option` is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Here is an example which increments every integer in a vector,</span>
<span class="doccomment">/// checking for overflow:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::u16;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let v = vec![1, 2];</span>
<span class="doccomment">/// let res: Option<Vec<u16>> = v.iter().map(|&x: &u16|</span>
<span class="doccomment">/// if x == u16::MAX { None }</span>
<span class="doccomment">/// else { Some(x + 1) }</span>
<span class="doccomment">/// ).collect();</span>
<span class="doccomment">/// assert!(res == Some(vec![2, 3]));</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Iterator`]: ../iter/trait.Iterator.html</span>
<span class="doccomment">/// [`None`]: enum.Option.html#variant.None</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">from_iter</span><span class="op"><</span><span class="ident">I</span>: <span class="ident">IntoIterator</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">A</span><span class="op">>></span><span class="op">></span>(<span class="ident">iter</span>: <span class="ident">I</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">V</span><span class="op">></span> {
<span class="comment">// FIXME(#11084): This could be replaced with Iterator::scan when this</span>
<span class="comment">// performance bug is closed.</span>
<span class="kw">struct</span> <span class="ident">Adapter</span><span class="op"><</span><span class="ident">Iter</span><span class="op">></span> {
<span class="ident">iter</span>: <span class="ident">Iter</span>,
<span class="ident">found_none</span>: <span class="ident">bool</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">Iter</span>: <span class="ident">Iterator</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">>></span><span class="op">></span> <span class="ident">Iterator</span> <span class="kw">for</span> <span class="ident">Adapter</span><span class="op"><</span><span class="ident">Iter</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">next</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">iter</span>.<span class="ident">next</span>() {
<span class="prelude-val">Some</span>(<span class="prelude-val">Some</span>(<span class="ident">value</span>)) <span class="op">=></span> <span class="prelude-val">Some</span>(<span class="ident">value</span>),
<span class="prelude-val">Some</span>(<span class="prelude-val">None</span>) <span class="op">=></span> {
<span class="self">self</span>.<span class="ident">found_none</span> <span class="op">=</span> <span class="bool-val">true</span>;
<span class="prelude-val">None</span>
}
<span class="prelude-val">None</span> <span class="op">=></span> <span class="prelude-val">None</span>,
}
}
}
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">adapter</span> <span class="op">=</span> <span class="ident">Adapter</span> { <span class="ident">iter</span>: <span class="ident">iter</span>.<span class="ident">into_iter</span>(), <span class="ident">found_none</span>: <span class="bool-val">false</span> };
<span class="kw">let</span> <span class="ident">v</span>: <span class="ident">V</span> <span class="op">=</span> <span class="ident">FromIterator</span>::<span class="ident">from_iter</span>(<span class="ident">adapter</span>.<span class="ident">by_ref</span>());
<span class="kw">if</span> <span class="ident">adapter</span>.<span class="ident">found_none</span> {
<span class="prelude-val">None</span>
} <span class="kw">else</span> {
<span class="prelude-val">Some</span>(<span class="ident">v</span>)
}
}
}
</pre>
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