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| <a name="Iterators-In-Guile"></a> |
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| <p> |
| Previous: <a href="Memory-Ports-in-Guile.html#Memory-Ports-in-Guile" accesskey="p" rel="prev">Memory Ports in Guile</a>, Up: <a href="Guile-API.html#Guile-API" accesskey="u" rel="up">Guile API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="Iterators-In-Guile-1"></a> |
| <h4 class="subsubsection">23.3.3.25 Iterators In Guile</h4> |
| |
| <a name="index-guile-iterators"></a> |
| <a name="index-_003cgdb_003aiterator_003e"></a> |
| |
| <p>A simple iterator facility is provided to allow, for example, |
| iterating over the set of program symbols without having to first |
| construct a list of all of them. A useful contribution would be |
| to add support for SRFI 41 and SRFI 45. |
| </p> |
| <dl> |
| <dt><a name="index-make_002diterator"></a>Scheme Procedure: <strong>make-iterator</strong> <em>object progress next!</em></dt> |
| <dd><p>A <code><gdb:iterator></code> object is constructed with the <code>make-iterator</code> |
| procedure. It takes three arguments: the object to be iterated over, |
| an object to record the progress of the iteration, and a procedure to |
| return the next element in the iteration, or an implementation chosen value |
| to denote the end of iteration. |
| </p> |
| <p>By convention, end of iteration is marked with <code>(end-of-iteration)</code>, |
| and may be tested with the <code>end-of-iteration?</code> predicate. |
| The result of <code>(end-of-iteration)</code> is chosen so that it is not |
| otherwise used by the <code>(gdb)</code> module. If you are using |
| <code><gdb:iterator></code> in your own code it is your responsibility to |
| maintain this invariant. |
| </p> |
| <p>A trivial example for illustration’s sake: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">(use-modules (gdb iterator)) |
| (define my-list (list 1 2 3)) |
| (define iter |
| (make-iterator my-list my-list |
| (lambda (iter) |
| (let ((l (iterator-progress iter))) |
| (if (eq? l '()) |
| (end-of-iteration) |
| (begin |
| (set-iterator-progress! iter (cdr l)) |
| (car l))))))) |
| </pre></div> |
| |
| <p>Here is a slightly more realistic example, which computes a list of all the |
| functions in <code>my-global-block</code>. |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">(use-modules (gdb iterator)) |
| (define this-sal (find-pc-line (frame-pc (selected-frame)))) |
| (define this-symtab (sal-symtab this-sal)) |
| (define this-global-block (symtab-global-block this-symtab)) |
| (define syms-iter (make-block-symbols-iterator this-global-block)) |
| (define functions (iterator-filter symbol-function? syms-iter)) |
| </pre></div> |
| </dd></dl> |
| |
| <dl> |
| <dt><a name="index-iterator_003f"></a>Scheme Procedure: <strong>iterator?</strong> <em>object</em></dt> |
| <dd><p>Return <code>#t</code> if <var>object</var> is a <code><gdb:iterator></code> object. |
| Otherwise return <code>#f</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-iterator_002dobject"></a>Scheme Procedure: <strong>iterator-object</strong> <em>iterator</em></dt> |
| <dd><p>Return the first argument that was passed to <code>make-iterator</code>. |
| This is the object being iterated over. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-iterator_002dprogress"></a>Scheme Procedure: <strong>iterator-progress</strong> <em>iterator</em></dt> |
| <dd><p>Return the object tracking iteration progress. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-set_002diterator_002dprogress_0021"></a>Scheme Procedure: <strong>set-iterator-progress!</strong> <em>iterator new-value</em></dt> |
| <dd><p>Set the object tracking iteration progress. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-iterator_002dnext_0021"></a>Scheme Procedure: <strong>iterator-next!</strong> <em>iterator</em></dt> |
| <dd><p>Invoke the procedure that was the third argument to <code>make-iterator</code>, |
| passing it one argument, the <code><gdb:iterator></code> object. |
| The result is either the next element in the iteration, or an end |
| marker as implemented by the <code>next!</code> procedure. |
| By convention the end marker is the result of <code>(end-of-iteration)</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-end_002dof_002diteration"></a>Scheme Procedure: <strong>end-of-iteration</strong></dt> |
| <dd><p>Return the Scheme object that denotes end of iteration. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-end_002dof_002diteration_003f"></a>Scheme Procedure: <strong>end-of-iteration?</strong> <em>object</em></dt> |
| <dd><p>Return <code>#t</code> if <var>object</var> is the end of iteration marker. |
| Otherwise return <code>#f</code>. |
| </p></dd></dl> |
| |
| <p>These functions are provided by the <code>(gdb iterator)</code> module to |
| assist in using iterators. |
| </p> |
| <dl> |
| <dt><a name="index-make_002dlist_002diterator"></a>Scheme Procedure: <strong>make-list-iterator</strong> <em>list</em></dt> |
| <dd><p>Return a <code><gdb:iterator></code> object that will iterate over <var>list</var>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-iterator_002d_003elist"></a>Scheme Procedure: <strong>iterator->list</strong> <em>iterator</em></dt> |
| <dd><p>Return the elements pointed to by <var>iterator</var> as a list. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-iterator_002dmap"></a>Scheme Procedure: <strong>iterator-map</strong> <em>proc iterator</em></dt> |
| <dd><p>Return the list of objects obtained by applying <var>proc</var> to the object |
| pointed to by <var>iterator</var> and to each subsequent object. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-iterator_002dfor_002deach"></a>Scheme Procedure: <strong>iterator-for-each</strong> <em>proc iterator</em></dt> |
| <dd><p>Apply <var>proc</var> to each element pointed to by <var>iterator</var>. |
| The result is unspecified. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-iterator_002dfilter"></a>Scheme Procedure: <strong>iterator-filter</strong> <em>pred iterator</em></dt> |
| <dd><p>Return the list of elements pointed to by <var>iterator</var> that satisfy |
| <var>pred</var>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-iterator_002duntil"></a>Scheme Procedure: <strong>iterator-until</strong> <em>pred iterator</em></dt> |
| <dd><p>Run <var>iterator</var> until the result of <code>(pred element)</code> is true |
| and return that as the result. Otherwise return <code>#f</code>. |
| </p></dd></dl> |
| |
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