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<center><h1>Module <a href="type_ListLabels.html">ListLabels</a></h1></center>
<br>
<pre><span class="keyword">module</span> ListLabels: <code class="code"><span class="keyword">sig</span></code> <a href="ListLabels.html">..</a> <code class="code"><span class="keyword">end</span></code></pre>List operations.
<p>
Some functions are flagged as not tail-recursive. A tail-recursive
function uses constant stack space, while a non-tail-recursive function
uses stack space proportional to the length of its list argument, which
can be a problem with very long lists. When the function takes several
list arguments, an approximate formula giving stack usage (in some
unspecified constant unit) is shown in parentheses.
<p>
The above considerations can usually be ignored if your lists are not
longer than about 10000 elements.<br>
<hr width="100%">
<pre><span class="keyword">val</span> <a name="VALlength"></a>length : <code class="type">'a list -> int</code></pre><div class="info">
Return the length (number of elements) of the given list.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALhd"></a>hd : <code class="type">'a list -> 'a</code></pre><div class="info">
Return the first element of the given list. Raise
<code class="code"><span class="constructor">Failure</span> <span class="string">"hd"</span></code> if the list is empty.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALtl"></a>tl : <code class="type">'a list -> 'a list</code></pre><div class="info">
Return the given list without its first element. Raise
<code class="code"><span class="constructor">Failure</span> <span class="string">"tl"</span></code> if the list is empty.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALnth"></a>nth : <code class="type">'a list -> int -> 'a</code></pre><div class="info">
Return the <code class="code">n</code>-th element of the given list.
The first element (head of the list) is at position 0.
Raise <code class="code"><span class="constructor">Failure</span> <span class="string">"nth"</span></code> if the list is too short.
Raise <code class="code"><span class="constructor">Invalid_argument</span> <span class="string">"List.nth"</span></code> if <code class="code">n</code> is negative.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALrev"></a>rev : <code class="type">'a list -> 'a list</code></pre><div class="info">
List reversal.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALappend"></a>append : <code class="type">'a list -> 'a list -> 'a list</code></pre><div class="info">
Catenate two lists. Same function as the infix operator <code class="code">@</code>.
Not tail-recursive (length of the first argument). The <code class="code">@</code>
operator is not tail-recursive either.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALrev_append"></a>rev_append : <code class="type">'a list -> 'a list -> 'a list</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.rev_append l1 l2</code> reverses <code class="code">l1</code> and concatenates it to <code class="code">l2</code>.
This is equivalent to <a href="ListLabels.html#VALrev"><code class="code"><span class="constructor">ListLabels</span>.rev</code></a><code class="code"> l1 @ l2</code>, but <code class="code">rev_append</code> is
tail-recursive and more efficient.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALconcat"></a>concat : <code class="type">'a list list -> 'a list</code></pre><div class="info">
Concatenate a list of lists. The elements of the argument are all
concatenated together (in the same order) to give the result.
Not tail-recursive
(length of the argument + length of the longest sub-list).<br>
</div>
<pre><span class="keyword">val</span> <a name="VALflatten"></a>flatten : <code class="type">'a list list -> 'a list</code></pre><div class="info">
Same as <code class="code">concat</code>. Not tail-recursive
(length of the argument + length of the longest sub-list).<br>
</div>
<br>
<a name="6_Iterators"></a>
<h6>Iterators</h6><br>
<pre><span class="keyword">val</span> <a name="VALiter"></a>iter : <code class="type">f:('a -> unit) -> 'a list -> unit</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.iter f [a1; ...; an]</code> applies function <code class="code">f</code> in turn to
<code class="code">a1; ...; an</code>. It is equivalent to
<code class="code"><span class="keyword">begin</span> f a1; f a2; ...; f an; () <span class="keyword">end</span></code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALmap"></a>map : <code class="type">f:('a -> 'b) -> 'a list -> 'b list</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.map f [a1; ...; an]</code> applies function <code class="code">f</code> to <code class="code">a1, ..., an</code>,
and builds the list <code class="code">[f a1; ...; f an]</code>
with the results returned by <code class="code">f</code>. Not tail-recursive.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALrev_map"></a>rev_map : <code class="type">f:('a -> 'b) -> 'a list -> 'b list</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.rev_map f l</code> gives the same result as
<a href="ListLabels.html#VALrev"><code class="code"><span class="constructor">ListLabels</span>.rev</code></a><code class="code"> (</code><a href="ListLabels.html#VALmap"><code class="code"><span class="constructor">ListLabels</span>.map</code></a><code class="code"> f l)</code>, but is tail-recursive and
more efficient.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALfold_left"></a>fold_left : <code class="type">f:('a -> 'b -> 'a) -> init:'a -> 'b list -> 'a</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.fold_left f a [b1; ...; bn]</code> is
<code class="code">f (... (f (f a b1) b2) ...) bn</code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALfold_right"></a>fold_right : <code class="type">f:('a -> 'b -> 'b) -> 'a list -> init:'b -> 'b</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.fold_right f [a1; ...; an] b</code> is
<code class="code">f a1 (f a2 (... (f an b) ...))</code>. Not tail-recursive.<br>
</div>
<br>
<a name="6_Iteratorsontwolists"></a>
<h6>Iterators on two lists</h6><br>
<pre><span class="keyword">val</span> <a name="VALiter2"></a>iter2 : <code class="type">f:('a -> 'b -> unit) -> 'a list -> 'b list -> unit</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.iter2 f [a1; ...; an] [b1; ...; bn]</code> calls in turn
<code class="code">f a1 b1; ...; f an bn</code>.
Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if the two lists have
different lengths.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALmap2"></a>map2 : <code class="type">f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.map2 f [a1; ...; an] [b1; ...; bn]</code> is
<code class="code">[f a1 b1; ...; f an bn]</code>.
Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if the two lists have
different lengths. Not tail-recursive.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALrev_map2"></a>rev_map2 : <code class="type">f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.rev_map2 f l1 l2</code> gives the same result as
<a href="ListLabels.html#VALrev"><code class="code"><span class="constructor">ListLabels</span>.rev</code></a><code class="code"> (</code><a href="ListLabels.html#VALmap2"><code class="code"><span class="constructor">ListLabels</span>.map2</code></a><code class="code"> f l1 l2)</code>, but is tail-recursive and
more efficient.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALfold_left2"></a>fold_left2 : <code class="type">f:('a -> 'b -> 'c -> 'a) -> init:'a -> 'b list -> 'c list -> 'a</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.fold_left2 f a [b1; ...; bn] [c1; ...; cn]</code> is
<code class="code">f (... (f (f a b1 c1) b2 c2) ...) bn cn</code>.
Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if the two lists have
different lengths.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALfold_right2"></a>fold_right2 : <code class="type">f:('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> init:'c -> 'c</code></pre><div class="info">
<code class="code"><span class="constructor">List</span>.fold_right2 f [a1; ...; an] [b1; ...; bn] c</code> is
<code class="code">f a1 b1 (f a2 b2 (... (f an bn c) ...))</code>.
Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if the two lists have
different lengths. Not tail-recursive.<br>
</div>
<br>
<a name="6_Listscanning"></a>
<h6>List scanning</h6><br>
<pre><span class="keyword">val</span> <a name="VALfor_all"></a>for_all : <code class="type">f:('a -> bool) -> 'a list -> bool</code></pre><div class="info">
<code class="code">for_all p [a1; ...; an]</code> checks if all elements of the list
satisfy the predicate <code class="code">p</code>. That is, it returns
<code class="code">(p a1) <span class="keywordsign">&&</span> (p a2) <span class="keywordsign">&&</span> ... <span class="keywordsign">&&</span> (p an)</code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALexists"></a>exists : <code class="type">f:('a -> bool) -> 'a list -> bool</code></pre><div class="info">
<code class="code">exists p [a1; ...; an]</code> checks if at least one element of
the list satisfies the predicate <code class="code">p</code>. That is, it returns
<code class="code">(p a1) <span class="keywordsign">||</span> (p a2) <span class="keywordsign">||</span> ... <span class="keywordsign">||</span> (p an)</code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALfor_all2"></a>for_all2 : <code class="type">f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool</code></pre><div class="info">
Same as <a href="ListLabels.html#VALfor_all"><code class="code"><span class="constructor">ListLabels</span>.for_all</code></a>, but for a two-argument predicate.
Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if the two lists have
different lengths.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALexists2"></a>exists2 : <code class="type">f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool</code></pre><div class="info">
Same as <a href="ListLabels.html#VALexists"><code class="code"><span class="constructor">ListLabels</span>.exists</code></a>, but for a two-argument predicate.
Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if the two lists have
different lengths.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALmem"></a>mem : <code class="type">'a -> set:'a list -> bool</code></pre><div class="info">
<code class="code">mem a l</code> is true if and only if <code class="code">a</code> is equal
to an element of <code class="code">l</code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALmemq"></a>memq : <code class="type">'a -> set:'a list -> bool</code></pre><div class="info">
Same as <a href="ListLabels.html#VALmem"><code class="code"><span class="constructor">ListLabels</span>.mem</code></a>, but uses physical equality instead of structural
equality to compare list elements.<br>
</div>
<br>
<a name="6_Listsearching"></a>
<h6>List searching</h6><br>
<pre><span class="keyword">val</span> <a name="VALfind"></a>find : <code class="type">f:('a -> bool) -> 'a list -> 'a</code></pre><div class="info">
<code class="code">find p l</code> returns the first element of the list <code class="code">l</code>
that satisfies the predicate <code class="code">p</code>.
Raise <code class="code"><span class="constructor">Not_found</span></code> if there is no value that satisfies <code class="code">p</code> in the
list <code class="code">l</code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALfilter"></a>filter : <code class="type">f:('a -> bool) -> 'a list -> 'a list</code></pre><div class="info">
<code class="code">filter p l</code> returns all the elements of the list <code class="code">l</code>
that satisfy the predicate <code class="code">p</code>. The order of the elements
in the input list is preserved.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALfind_all"></a>find_all : <code class="type">f:('a -> bool) -> 'a list -> 'a list</code></pre><div class="info">
<code class="code">find_all</code> is another name for <a href="ListLabels.html#VALfilter"><code class="code"><span class="constructor">ListLabels</span>.filter</code></a>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALpartition"></a>partition : <code class="type">f:('a -> bool) -> 'a list -> 'a list * 'a list</code></pre><div class="info">
<code class="code">partition p l</code> returns a pair of lists <code class="code">(l1, l2)</code>, where
<code class="code">l1</code> is the list of all the elements of <code class="code">l</code> that
satisfy the predicate <code class="code">p</code>, and <code class="code">l2</code> is the list of all the
elements of <code class="code">l</code> that do not satisfy <code class="code">p</code>.
The order of the elements in the input list is preserved.<br>
</div>
<br>
<a name="6_Associationlists"></a>
<h6>Association lists</h6><br>
<pre><span class="keyword">val</span> <a name="VALassoc"></a>assoc : <code class="type">'a -> ('a * 'b) list -> 'b</code></pre><div class="info">
<code class="code">assoc a l</code> returns the value associated with key <code class="code">a</code> in the list of
pairs <code class="code">l</code>. That is,
<code class="code">assoc a [ ...; (a,b); ...] = b</code>
if <code class="code">(a,b)</code> is the leftmost binding of <code class="code">a</code> in list <code class="code">l</code>.
Raise <code class="code"><span class="constructor">Not_found</span></code> if there is no value associated with <code class="code">a</code> in the
list <code class="code">l</code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALassq"></a>assq : <code class="type">'a -> ('a * 'b) list -> 'b</code></pre><div class="info">
Same as <a href="ListLabels.html#VALassoc"><code class="code"><span class="constructor">ListLabels</span>.assoc</code></a>, but uses physical equality instead of
structural equality to compare keys.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALmem_assoc"></a>mem_assoc : <code class="type">'a -> map:('a * 'b) list -> bool</code></pre><div class="info">
Same as <a href="ListLabels.html#VALassoc"><code class="code"><span class="constructor">ListLabels</span>.assoc</code></a>, but simply return true if a binding exists,
and false if no bindings exist for the given key.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALmem_assq"></a>mem_assq : <code class="type">'a -> map:('a * 'b) list -> bool</code></pre><div class="info">
Same as <a href="ListLabels.html#VALmem_assoc"><code class="code"><span class="constructor">ListLabels</span>.mem_assoc</code></a>, but uses physical equality instead of
structural equality to compare keys.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALremove_assoc"></a>remove_assoc : <code class="type">'a -> ('a * 'b) list -> ('a * 'b) list</code></pre><div class="info">
<code class="code">remove_assoc a l</code> returns the list of
pairs <code class="code">l</code> without the first pair with key <code class="code">a</code>, if any.
Not tail-recursive.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALremove_assq"></a>remove_assq : <code class="type">'a -> ('a * 'b) list -> ('a * 'b) list</code></pre><div class="info">
Same as <a href="ListLabels.html#VALremove_assoc"><code class="code"><span class="constructor">ListLabels</span>.remove_assoc</code></a>, but uses physical equality instead
of structural equality to compare keys. Not tail-recursive.<br>
</div>
<br>
<a name="6_Listsofpairs"></a>
<h6>Lists of pairs</h6><br>
<pre><span class="keyword">val</span> <a name="VALsplit"></a>split : <code class="type">('a * 'b) list -> 'a list * 'b list</code></pre><div class="info">
Transform a list of pairs into a pair of lists:
<code class="code">split [(a1,b1); ...; (an,bn)]</code> is <code class="code">([a1; ...; an], [b1; ...; bn])</code>.
Not tail-recursive.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALcombine"></a>combine : <code class="type">'a list -> 'b list -> ('a * 'b) list</code></pre><div class="info">
Transform a pair of lists into a list of pairs:
<code class="code">combine [a1; ...; an] [b1; ...; bn]</code> is
<code class="code">[(a1,b1); ...; (an,bn)]</code>.
Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if the two lists
have different lengths. Not tail-recursive.<br>
</div>
<br>
<a name="6_Sorting"></a>
<h6>Sorting</h6><br>
<pre><span class="keyword">val</span> <a name="VALsort"></a>sort : <code class="type">cmp:('a -> 'a -> int) -> 'a list -> 'a list</code></pre><div class="info">
Sort a list in increasing order according to a comparison
function. The comparison function must return 0 if its arguments
compare as equal, a positive integer if the first is greater,
and a negative integer if the first is smaller (see Array.sort for
a complete specification). For example,
<a href="Pervasives.html#VALcompare"><code class="code">compare</code></a> is a suitable comparison function.
The resulting list is sorted in increasing order.
<code class="code"><span class="constructor">List</span>.sort</code> is guaranteed to run in constant heap space
(in addition to the size of the result list) and logarithmic
stack space.
<p>
The current implementation uses Merge Sort. It runs in constant
heap space and logarithmic stack space.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALstable_sort"></a>stable_sort : <code class="type">cmp:('a -> 'a -> int) -> 'a list -> 'a list</code></pre><div class="info">
Same as <a href="ListLabels.html#VALsort"><code class="code"><span class="constructor">ListLabels</span>.sort</code></a>, but the sorting algorithm is guaranteed to
be stable (i.e. elements that compare equal are kept in their
original order) .
<p>
The current implementation uses Merge Sort. It runs in constant
heap space and logarithmic stack space.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALfast_sort"></a>fast_sort : <code class="type">cmp:('a -> 'a -> int) -> 'a list -> 'a list</code></pre><div class="info">
Same as <a href="List.html#VALsort"><code class="code"><span class="constructor">List</span>.sort</code></a> or <a href="List.html#VALstable_sort"><code class="code"><span class="constructor">List</span>.stable_sort</code></a>, whichever is faster
on typical input.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALmerge"></a>merge : <code class="type">cmp:('a -> 'a -> int) -> 'a list -> 'a list -> 'a list</code></pre><div class="info">
Merge two lists:
Assuming that <code class="code">l1</code> and <code class="code">l2</code> are sorted according to the
comparison function <code class="code">cmp</code>, <code class="code">merge cmp l1 l2</code> will return a
sorted list containting all the elements of <code class="code">l1</code> and <code class="code">l2</code>.
If several elements compare equal, the elements of <code class="code">l1</code> will be
before the elements of <code class="code">l2</code>.
Not tail-recursive (sum of the lengths of the arguments).<br>
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