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177 lines
8.4 KiB
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<html lang="en">
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<title>Iterators In Guile - Debugging with GDB</title>
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<meta name="description" content="Debugging with GDB">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Guile-API.html#Guile-API" title="Guile API">
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<link rel="prev" href="Memory-Ports-in-Guile.html#Memory-Ports-in-Guile" title="Memory Ports in Guile">
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
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</head>
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<body>
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<div class="node">
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<a name="Iterators-In-Guile"></a>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Memory-Ports-in-Guile.html#Memory-Ports-in-Guile">Memory Ports in Guile</a>,
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Up: <a rel="up" accesskey="u" href="Guile-API.html#Guile-API">Guile API</a>
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<hr>
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</div>
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<h5 class="subsubsection">23.3.3.25 Iterators In Guile</h5>
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<p><a name="index-guile-iterators-2855"></a><a name="index-g_t_003cgdb_003aiterator_003e-2856"></a>
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A simple iterator facility is provided to allow, for example,
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iterating over the set of program symbols without having to first
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construct a list of all of them. A useful contribution would be
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to add support for SRFI 41 and SRFI 45.
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<div class="defun">
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— Scheme Procedure: <b>make-iterator</b><var> object progress next!<a name="index-make_002diterator-2857"></a></var><br>
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<blockquote><p>A <code><gdb:iterator></code> object is constructed with the <code>make-iterator</code>
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procedure. It takes three arguments: the object to be iterated over,
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an object to record the progress of the iteration, and a procedure to
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return the next element in the iteration, or an implementation chosen value
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to denote the end of iteration.
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<p>By convention, end of iteration is marked with <code>(end-of-iteration)</code>,
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and may be tested with the <code>end-of-iteration?</code> predicate.
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The result of <code>(end-of-iteration)</code> is chosen so that it is not
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otherwise used by the <code>(gdb)</code> module. If you are using
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<code><gdb:iterator></code> in your own code it is your responsibility to
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maintain this invariant.
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<p>A trivial example for illustration's sake:
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<pre class="smallexample"> (use-modules (gdb iterator))
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(define my-list (list 1 2 3))
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(define iter
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(make-iterator my-list my-list
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(lambda (iter)
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(let ((l (iterator-progress iter)))
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(if (eq? l '())
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(end-of-iteration)
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(begin
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(set-iterator-progress! iter (cdr l))
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(car l)))))))
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</pre>
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<p>Here is a slightly more realistic example, which computes a list of all the
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functions in <code>my-global-block</code>.
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<pre class="smallexample"> (use-modules (gdb iterator))
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(define this-sal (find-pc-line (frame-pc (selected-frame))))
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(define this-symtab (sal-symtab this-sal))
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(define this-global-block (symtab-global-block this-symtab))
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(define syms-iter (make-block-symbols-iterator this-global-block))
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(define functions (iterator-filter symbol-function? syms-iter))
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</pre>
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</blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>iterator?</b><var> object<a name="index-iterator_003f-2858"></a></var><br>
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<blockquote><p>Return <code>#t</code> if <var>object</var> is a <code><gdb:iterator></code> object.
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Otherwise return <code>#f</code>.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>iterator-object</b><var> iterator<a name="index-iterator_002dobject-2859"></a></var><br>
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<blockquote><p>Return the first argument that was passed to <code>make-iterator</code>.
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This is the object being iterated over.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>iterator-progress</b><var> iterator<a name="index-iterator_002dprogress-2860"></a></var><br>
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<blockquote><p>Return the object tracking iteration progress.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>set-iterator-progress!</b><var> iterator new-value<a name="index-set_002diterator_002dprogress_0021-2861"></a></var><br>
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<blockquote><p>Set the object tracking iteration progress.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>iterator-next!</b><var> iterator<a name="index-iterator_002dnext_0021-2862"></a></var><br>
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<blockquote><p>Invoke the procedure that was the third argument to <code>make-iterator</code>,
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passing it one argument, the <code><gdb:iterator></code> object.
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The result is either the next element in the iteration, or an end
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marker as implemented by the <code>next!</code> procedure.
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By convention the end marker is the result of <code>(end-of-iteration)</code>.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>end-of-iteration</b><var><a name="index-end_002dof_002diteration-2863"></a></var><br>
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<blockquote><p>Return the Scheme object that denotes end of iteration.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>end-of-iteration?</b><var> object<a name="index-end_002dof_002diteration_003f-2864"></a></var><br>
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<blockquote><p>Return <code>#t</code> if <var>object</var> is the end of iteration marker.
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Otherwise return <code>#f</code>.
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</p></blockquote></div>
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<p>These functions are provided by the <code>(gdb iterator)</code> module to
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assist in using iterators.
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<div class="defun">
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— Scheme Procedure: <b>make-list-iterator</b><var> list<a name="index-make_002dlist_002diterator-2865"></a></var><br>
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<blockquote><p>Return a <code><gdb:iterator></code> object that will iterate over <var>list</var>.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>iterator->list</b><var> iterator<a name="index-iterator_002d_003elist-2866"></a></var><br>
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<blockquote><p>Return the elements pointed to by <var>iterator</var> as a list.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>iterator-map</b><var> proc iterator<a name="index-iterator_002dmap-2867"></a></var><br>
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<blockquote><p>Return the list of objects obtained by applying <var>proc</var> to the object
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pointed to by <var>iterator</var> and to each subsequent object.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>iterator-for-each</b><var> proc iterator<a name="index-iterator_002dfor_002deach-2868"></a></var><br>
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<blockquote><p>Apply <var>proc</var> to each element pointed to by <var>iterator</var>.
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The result is unspecified.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>iterator-filter</b><var> pred iterator<a name="index-iterator_002dfilter-2869"></a></var><br>
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<blockquote><p>Return the list of elements pointed to by <var>iterator</var> that satisfy
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<var>pred</var>.
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</p></blockquote></div>
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<div class="defun">
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— Scheme Procedure: <b>iterator-until</b><var> pred iterator<a name="index-iterator_002duntil-2870"></a></var><br>
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<blockquote><p>Run <var>iterator</var> until the result of <code>(pred element)</code> is true
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and return that as the result. Otherwise return <code>#f</code>.
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</p></blockquote></div>
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