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<ol class="chapter"><li class="affix"><a href="introduction.html">Introduction</a></li><li><a href="notation.html"><strong aria-hidden="true">1.</strong> Notation</a></li><li><a href="lexical-structure.html"><strong aria-hidden="true">2.</strong> Lexical structure</a></li><li><ol class="section"><li><a href="input-format.html"><strong aria-hidden="true">2.1.</strong> Input format</a></li><li><a href="keywords.html"><strong aria-hidden="true">2.2.</strong> Keywords</a></li><li><a href="identifiers.html"><strong aria-hidden="true">2.3.</strong> Identifiers</a></li><li><a href="comments.html"><strong aria-hidden="true">2.4.</strong> Comments</a></li><li><a href="whitespace.html"><strong aria-hidden="true">2.5.</strong> Whitespace</a></li><li><a href="tokens.html"><strong aria-hidden="true">2.6.</strong> Tokens</a></li><li><a href="paths.html"><strong aria-hidden="true">2.7.</strong> Paths</a></li></ol></li><li><a href="macros.html"><strong aria-hidden="true">3.</strong> Macros</a></li><li><ol class="section"><li><a href="macros-by-example.html"><strong aria-hidden="true">3.1.</strong> Macros By Example</a></li><li><a href="procedural-macros.html"><strong aria-hidden="true">3.2.</strong> Procedural Macros</a></li></ol></li><li><a href="crates-and-source-files.html"><strong aria-hidden="true">4.</strong> Crates and source files</a></li><li><a href="items-and-attributes.html"><strong aria-hidden="true">5.</strong> Items and attributes</a></li><li><ol class="section"><li><a href="items.html"><strong aria-hidden="true">5.1.</strong> Items</a></li><li><ol class="section"><li><a href="items/modules.html"><strong aria-hidden="true">5.1.1.</strong> Modules</a></li><li><a href="items/extern-crates.html"><strong aria-hidden="true">5.1.2.</strong> Extern crates</a></li><li><a href="items/use-declarations.html"><strong aria-hidden="true">5.1.3.</strong> Use declarations</a></li><li><a href="items/functions.html"><strong aria-hidden="true">5.1.4.</strong> Functions</a></li><li><a href="items/type-aliases.html"><strong aria-hidden="true">5.1.5.</strong> Type aliases</a></li><li><a href="items/structs.html"><strong aria-hidden="true">5.1.6.</strong> Structs</a></li><li><a href="items/enumerations.html"><strong aria-hidden="true">5.1.7.</strong> Enumerations</a></li><li><a href="items/unions.html"><strong aria-hidden="true">5.1.8.</strong> Unions</a></li><li><a href="items/constant-items.html"><strong aria-hidden="true">5.1.9.</strong> Constant items</a></li><li><a href="items/static-items.html"><strong aria-hidden="true">5.1.10.</strong> Static items</a></li><li><a href="items/traits.html"><strong aria-hidden="true">5.1.11.</strong> Traits</a></li><li><a href="items/implementations.html"><strong aria-hidden="true">5.1.12.</strong> Implementations</a></li><li><a href="items/external-blocks.html"><strong aria-hidden="true">5.1.13.</strong> External blocks</a></li></ol></li><li><a href="items/generics.html"><strong aria-hidden="true">5.2.</strong> Type and lifetime parameters</a></li><li><a href="items/associated-items.html"><strong aria-hidden="true">5.3.</strong> Associated Items</a></li><li><a href="visibility-and-privacy.html"><strong aria-hidden="true">5.4.</strong> Visibility and Privacy</a></li><li><a href="attributes.html"><strong aria-hidden="true">5.5.</strong> Attributes</a></li></ol></li><li><a href="statements-and-expressions.html"><strong aria-hidden="true">6.</strong> Statements and expressions</a></li><li><ol class="section"><li><a href="statements.html"><strong aria-hidden="true">6.1.</strong> Statements</a></li><li><a href="expressions.html"><strong aria-hidden="true">6.2.</strong> Expressions</a></li><li><ol class="section"><li><a href="expressions/literal-expr.html"><strong aria-hidden="true">6.2.1.</strong> Literal expressions</a></li><li><a href="expressions/path-expr.html"><strong aria-hidden="true">6.2.2.</strong> Path expressions</a></li><li><a href="expressions/block-expr.html"><strong aria-hidden="true">6.2.3.</strong> Block expressions</a></li><li><a href="expressions/operator-expr.html"><strong aria-hidden="true">6.2.4.</strong> Operator expressions</a></li><li><a href="expressions/grouped-expr.html"><strong aria-hidden="true">6.2.5.</strong> Grouped expressions</a></li><li><a href="expressions/array-expr.html"><strong aria-hidden="true">6.2.6.</strong> Array and index expressions</a></li><li><a href="expressions/tuple-expr.html"><strong aria-hidden="true">6.2.7.</strong> Tuple and index expressions</a></li><li><a href="expressions/struct-expr.html"><strong aria-hidden="true">6.2.8.</strong> Struct expressions</a></li><li><a href="expressions/enum-variant-expr.html"><strong aria-hidden="true">6.2.9.</strong> Enum variant expressions</a></li><li><a href="expressions/call-expr.html"><strong aria-hidden="true">6.2.10.</strong> Call expressions</a></li><li><a href="expressions/method-call-expr.html"><strong aria-hidden="true">6.2.11.</strong> Method call expressions</a></li><li><a href="expressions/field-expr.html"><strong aria-hidden="true">6.2.12.</strong> Field access expressions</a></li><li><a href="expressions/closure-expr.html"><strong aria-hidden="true">6.2.13.</strong> Closure expressions</a></li><li><a href="expressions/loop-expr.html"><strong aria-hidden="true">6.2.14.</strong> Loop expressions</a></li><li><a href="expressions/range-expr.html"><strong aria-hidden="true">6.2.15.</strong> Range expressions</a></li><li><a href="expressions/if-expr.html"><strong aria-hidden="true">6.2.16.</strong> If and if let expressions</a></li><li><a href="expressions/match-expr.html"><strong aria-hidden="true">6.2.17.</strong> Match expressions</a></li><li><a href="expressions/return-expr.html"><strong aria-hidden="true">6.2.18.</strong> Return expressions</a></li></ol></li></ol></li><li><a href="type-system.html"><strong aria-hidden="true">7.</strong> Type system</a></li><li><ol class="section"><li><a href="types.html"><strong aria-hidden="true">7.1.</strong> Types</a></li><li><a href="dynamically-sized-types.html"><strong aria-hidden="true">7.2.</strong> Dynamically Sized Types</a></li><li><a href="type-layout.html"><strong aria-hidden="true">7.3.</strong> Type layout</a></li><li><a href="interior-mutability.html"><strong aria-hidden="true">7.4.</strong> Interior mutability</a></li><li><a href="subtyping.html"><strong aria-hidden="true">7.5.</strong> Subtyping and Variance</a></li><li><a href="trait-bounds.html"><strong aria-hidden="true">7.6.</strong> Trait and lifetime bounds</a></li><li><a href="type-coercions.html"><strong aria-hidden="true">7.7.</strong> Type coercions</a></li><li><a href="destructors.html"><strong aria-hidden="true">7.8.</strong> Destructors</a></li><li><a href="lifetime-elision.html"><strong aria-hidden="true">7.9.</strong> Lifetime elision</a></li></ol></li><li><a href="special-types-and-traits.html"><strong aria-hidden="true">8.</strong> Special types and traits</a></li><li><a href="memory-model.html"><strong aria-hidden="true">9.</strong> Memory model</a></li><li><ol class="section"><li><a href="memory-allocation-and-lifetime.html"><strong aria-hidden="true">9.1.</strong> Memory allocation and lifetime</a></li><li><a href="memory-ownership.html"><strong aria-hidden="true">9.2.</strong> Memory ownership</a></li><li><a href="variables.html"><strong aria-hidden="true">9.3.</strong> Variables</a></li></ol></li><li><a href="linkage.html"><strong aria-hidden="true">10.</strong> Linkage</a></li><li><a href="unsafety.html"><strong aria-hidden="true">11.</strong> Unsafety</a></li><li><ol class="section"><li><a href="unsafe-functions.html"><strong aria-hidden="true">11.1.</strong> Unsafe functions</a></li><li><a href="unsafe-blocks.html"><strong aria-hidden="true">11.2.</strong> Unsafe blocks</a></li><li><a href="behavior-considered-undefined.html"><strong aria-hidden="true">11.3.</strong> Behavior considered undefined</a></li><li><a href="behavior-not-considered-unsafe.html"><strong aria-hidden="true">11.4.</strong> Behavior not considered unsafe</a></li></ol></li><li><a href="influences.html">Appendix: Influences</a></li><li class="affix"><a href="undocumented.html">Appendix: As-yet-undocumented Features</a></li><li class="affix"><a href="glossary.html" class="active">Appendix: Glossary</a></li></ol>
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<a class="header" href="glossary.html#glossary" id="glossary"><h1>Glossary</h1></a>
<a class="header" href="glossary.html#abstract-syntax-tree" id="abstract-syntax-tree"><h3>Abstract Syntax Tree</h3></a>
<p>An ‘abstract syntax tree’, or ‘AST’, is an intermediate representation of
the structure of the program when the compiler is compiling it.</p>
<a class="header" href="glossary.html#alignment" id="alignment"><h3>Alignment</h3></a>
<p>The alignment of a value specifies what addresses values are preferred to
start at. Always a power of two. References to a value must be aligned.
<a href="type-layout.html#size-and-alignment">More</a>.</p>
<a class="header" href="glossary.html#arity" id="arity"><h3>Arity</h3></a>
<p>Arity refers to the number of arguments a function or operator takes.
For some examples, <code>f(2, 3)</code> and <code>g(4, 6)</code> have arity 2, while <code>h(8, 2, 6)</code>
has arity 3. The <code>!</code> operator has arity 1.</p>
<a class="header" href="glossary.html#array" id="array"><h3>Array</h3></a>
<p>An array, sometimes also called a fixed-size array or an inline array, is a value
describing a collection of elements, each selected by an index that can be computed
at run time by the program. It occupies a contiguous region of memory.</p>
<a class="header" href="glossary.html#associated-item" id="associated-item"><h3>Associated Item</h3></a>
<p>An associated item is an item that is associated with another item. Associated
items are defined in <a href="items/implementations.html">implementations</a> and declared in <a href="items/traits.html">traits</a>. Only functions,
constants, and type aliases can be associated.</p>
<a class="header" href="glossary.html#bound" id="bound"><h3>Bound</h3></a>
<p>Bounds are constraints on a type or trait. For example, if a bound
is placed on the argument a function takes, types passed to that function
must abide by that constraint.</p>
<a class="header" href="glossary.html#combinator" id="combinator"><h3>Combinator</h3></a>
<p>Combinators are higher-order functions that apply only functions and
earlier defined combinators to provide a result from its arguments.
They can be used to manage control flow in a modular fashion.</p>
<a class="header" href="glossary.html#dispatch" id="dispatch"><h3>Dispatch</h3></a>
<p>Dispatch is the mechanism to determine which specific version of code is actually
run when it involves polymorphism. Two major forms of dispatch are static dispatch and
dynamic dispatch. While Rust favors static dispatch, it also supports dynamic dispatch
through a mechanism called ‘trait objects’.</p>
<a class="header" href="glossary.html#dynamically-sized-type" id="dynamically-sized-type"><h3>Dynamically Sized Type</h3></a>
<p>A dynamically sized type (DST) is a type without a statically known size or alignment.</p>
<a class="header" href="glossary.html#expression" id="expression"><h3>Expression</h3></a>
<p>An expression is a combination of values, constants, variables, operators
and functions that evaluate to a single value, with or without side-effects.</p>
<p>For example, <code>2 + (3 * 4)</code> is an expression that returns the value 14.</p>
<a class="header" href="glossary.html#initialized" id="initialized"><h3>Initialized</h3></a>
<p>A variable is initialized if it has been assigned a value and hasn't since been
moved from. All other memory locations are assumed to be initialized. Only
unsafe Rust can create such a memory without initializing it.</p>
<a class="header" href="glossary.html#nominal-types" id="nominal-types"><h3>Nominal Types</h3></a>
<p>Types that can be referred to by a path directly. Specifically <a href="items/enumerations.html">enums</a>,
<a href="items/structs.html">structs</a>, <a href="items/unions.html">unions</a>, and <a href="types.html#trait-objects">trait objects</a>.</p>
<a class="header" href="glossary.html#object-safe-traits" id="object-safe-traits"><h3>Object Safe Traits</h3></a>
<p><a href="items/traits.html">Traits</a> that can be used as <a href="types.html#trait-objects">trait objects</a>. Only traits that follow specific
<a href="items/traits.html#object-safety">rules</a> are object safe.</p>
<a class="header" href="glossary.html#prelude" id="prelude"><h3>Prelude</h3></a>
<p>Prelude, or The Rust Prelude, is a small collection of items - mostly traits - that are
imported into every module of every crate. The traits in the prelude are pervasive.</p>
<a class="header" href="glossary.html#size" id="size"><h3>Size</h3></a>
<p>The size of a value has two definitions.</p>
<p>The first is that it is how much memory must be allocated to store that value.</p>
<p>The second is that it is the offset in bytes between successive elements in an
array with that item type.</p>
<p>It is a multiple of the alignment, including zero. The size can change
depending on compiler version (as new optimizations are made) and target
platform (similar to how <code>usize</code> varies per-platform).</p>
<p><a href="type-layout.html#size-and-alignment">More</a>.</p>
<a class="header" href="glossary.html#slice" id="slice"><h3>Slice</h3></a>
<p>A slice is dynamically-sized view into a contiguous sequence, written as <code>[T]</code>.</p>
<p>It is often seen in its borrowed forms, either mutable or shared. The shared
slice type is <code>&[T]</code>, while the mutable slice type is <code>&mut [T]</code>, where <code>T</code> represents
the element type.</p>
<a class="header" href="glossary.html#statement" id="statement"><h3>Statement</h3></a>
<p>A statement is the smallest standalone element of a programming language
that commands a computer to perform an action.</p>
<a class="header" href="glossary.html#string-literal" id="string-literal"><h3>String literal</h3></a>
<p>A string literal is a string stored directly in the final binary, and so will be
valid for the <code>'static</code> duration.</p>
<p>Its type is <code>'static</code> duration borrowed string slice, <code>&'static str</code>.</p>
<a class="header" href="glossary.html#string-slice" id="string-slice"><h3>String slice</h3></a>
<p>A string slice is the most primitive string type in Rust, written as <code>str</code>. It is
often seen in its borrowed forms, either mutable or shared. The shared
string slice type is <code>&str</code>, while the mutable string slice type is <code>&mut str</code>.</p>
<p>Strings slices are always valid UTF-8.</p>
<a class="header" href="glossary.html#trait" id="trait"><h3>Trait</h3></a>
<p>A trait is a language item that is used for describing the functionalities a type must provide.
It allows a type to make certain promises about its behavior.</p>
<p>Generic functions and generic structs can use traits to constrain, or bound, the types they accept.</p>
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