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href="Tk.html"> <link title="Unix" rel="Chapter" href="Unix.html"> <link title="UnixLabels" rel="Chapter" href="UnixLabels.html"> <link title="Weak" rel="Chapter" href="Weak.html"><title>Queue</title> </head> <body> <div class="navbar"><a class="pre" href="Printf.html" title="Printf">Previous</a> <a class="up" href="index.html" title="Index">Up</a> <a class="post" href="Random.html" title="Random">Next</a> </div> <h1>Module <a href="type_Queue.html">Queue</a></h1> <pre><span class="keyword">module</span> Queue: <code class="code"><span class="keyword">sig</span></code> <a href="Queue.html">..</a> <code class="code"><span class="keyword">end</span></code></pre><div class="info module top"> First-in first-out queues. <p> This module implements queues (FIFOs), with in-place modification. <p> <b>Warning</b> This module is not thread-safe: each <a href="Queue.html#TYPEt"><code class="code"><span class="constructor">Queue</span>.t</code></a> value must be protected from concurrent access (e.g. with a <a href="Mutex.html#TYPEt"><code class="code"><span class="constructor">Mutex</span>.t</code></a>). Failure to do so can lead to a crash.<br> </div> <hr width="100%"> <pre><span id="TYPEt"><span class="keyword">type</span> <code class="type">'a</code> t</span> </pre> <div class="info "> The type of queues containing elements of type <code class="code"><span class="keywordsign">'</span>a</code>.<br> </div> <pre><span id="EXCEPTIONEmpty"><span class="keyword">exception</span> Empty</span></pre> <div class="info "> Raised when <a href="Queue.html#VALtake"><code class="code"><span class="constructor">Queue</span>.take</code></a> or <a href="Queue.html#VALpeek"><code class="code"><span class="constructor">Queue</span>.peek</code></a> is applied to an empty queue.<br> </div> <pre><span id="VALcreate"><span class="keyword">val</span> create</span> : <code class="type">unit -> 'a <a href="Queue.html#TYPEt">t</a></code></pre><div class="info "> Return a new queue, initially empty.<br> </div> <pre><span id="VALadd"><span class="keyword">val</span> add</span> : <code class="type">'a -> 'a <a href="Queue.html#TYPEt">t</a> -> unit</code></pre><div class="info "> <code class="code">add x q</code> adds the element <code class="code">x</code> at the end of the queue <code class="code">q</code>.<br> </div> <pre><span id="VALpush"><span class="keyword">val</span> push</span> : <code class="type">'a -> 'a <a href="Queue.html#TYPEt">t</a> -> unit</code></pre><div class="info "> <code class="code">push</code> is a synonym for <code class="code">add</code>.<br> </div> <pre><span id="VALtake"><span class="keyword">val</span> take</span> : <code class="type">'a <a href="Queue.html#TYPEt">t</a> -> 'a</code></pre><div class="info "> <code class="code">take q</code> removes and returns the first element in queue <code class="code">q</code>, or raises <code class="code"><span class="constructor">Empty</span></code> if the queue is empty.<br> </div> <pre><span id="VALpop"><span class="keyword">val</span> pop</span> : <code class="type">'a <a href="Queue.html#TYPEt">t</a> -> 'a</code></pre><div class="info "> <code class="code">pop</code> is a synonym for <code class="code">take</code>.<br> </div> <pre><span id="VALpeek"><span class="keyword">val</span> peek</span> : <code class="type">'a <a href="Queue.html#TYPEt">t</a> -> 'a</code></pre><div class="info "> <code class="code">peek q</code> returns the first element in queue <code class="code">q</code>, without removing it from the queue, or raises <code class="code"><span class="constructor">Empty</span></code> if the queue is empty.<br> </div> <pre><span id="VALtop"><span class="keyword">val</span> top</span> : <code class="type">'a <a href="Queue.html#TYPEt">t</a> -> 'a</code></pre><div class="info "> <code class="code">top</code> is a synonym for <code class="code">peek</code>.<br> </div> <pre><span id="VALclear"><span class="keyword">val</span> clear</span> : <code class="type">'a <a href="Queue.html#TYPEt">t</a> -> unit</code></pre><div class="info "> Discard all elements from a queue.<br> </div> <pre><span id="VALcopy"><span class="keyword">val</span> copy</span> : <code class="type">'a <a href="Queue.html#TYPEt">t</a> -> 'a <a href="Queue.html#TYPEt">t</a></code></pre><div class="info "> Return a copy of the given queue.<br> </div> <pre><span id="VALis_empty"><span class="keyword">val</span> is_empty</span> : <code class="type">'a <a href="Queue.html#TYPEt">t</a> -> bool</code></pre><div class="info "> Return <code class="code"><span class="keyword">true</span></code> if the given queue is empty, <code class="code"><span class="keyword">false</span></code> otherwise.<br> </div> <pre><span id="VALlength"><span class="keyword">val</span> length</span> : <code class="type">'a <a href="Queue.html#TYPEt">t</a> -> int</code></pre><div class="info "> Return the number of elements in a queue.<br> </div> <pre><span id="VALiter"><span class="keyword">val</span> iter</span> : <code class="type">('a -> unit) -> 'a <a href="Queue.html#TYPEt">t</a> -> unit</code></pre><div class="info "> <code class="code">iter f q</code> applies <code class="code">f</code> in turn to all elements of <code class="code">q</code>, from the least recently entered to the most recently entered. The queue itself is unchanged.<br> </div> <pre><span id="VALfold"><span class="keyword">val</span> fold</span> : <code class="type">('b -> 'a -> 'b) -> 'b -> 'a <a href="Queue.html#TYPEt">t</a> -> 'b</code></pre><div class="info "> <code class="code">fold f accu q</code> is equivalent to <code class="code"><span class="constructor">List</span>.fold_left f accu l</code>, where <code class="code">l</code> is the list of <code class="code">q</code>'s elements. The queue remains unchanged.<br> </div> <pre><span id="VALtransfer"><span class="keyword">val</span> transfer</span> : <code class="type">'a <a href="Queue.html#TYPEt">t</a> -> 'a <a href="Queue.html#TYPEt">t</a> -> unit</code></pre><div class="info "> <code class="code">transfer q1 q2</code> adds all of <code class="code">q1</code>'s elements at the end of the queue <code class="code">q2</code>, then clears <code class="code">q1</code>. It is equivalent to the sequence <code class="code">iter (<span class="keyword">fun</span> x <span class="keywordsign">-></span> add x q2) q1; clear q1</code>, but runs in constant time.<br> </div> </body></html>