<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <!-- Copyright (C) 1988-2019 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being "Free Software" and "Free Software Needs Free Documentation", with the Front-Cover Texts being "A GNU Manual," and with the Back-Cover Texts as in (a) below. (a) The FSF's Back-Cover Text is: "You are free to copy and modify this GNU Manual. Buying copies from GNU Press supports the FSF in developing GNU and promoting software freedom." --> <!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ --> <head> <title>Iterators In Guile (Debugging with GDB)</title> <meta name="description" content="Iterators In Guile (Debugging with GDB)"> <meta name="keywords" content="Iterators In Guile (Debugging with GDB)"> <meta name="resource-type" content="document"> <meta name="distribution" content="global"> <meta name="Generator" content="makeinfo"> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <link href="index.html#Top" rel="start" title="Top"> <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> <link href="Guile-API.html#Guile-API" rel="up" title="Guile API"> <link href="Guile-Auto_002dloading.html#Guile-Auto_002dloading" rel="next" title="Guile Auto-loading"> <link href="Memory-Ports-in-Guile.html#Memory-Ports-in-Guile" rel="prev" title="Memory Ports in Guile"> <style type="text/css"> <!-- a.summary-letter {text-decoration: none} blockquote.indentedblock {margin-right: 0em} blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} blockquote.smallquotation {font-size: smaller} div.display {margin-left: 3.2em} div.example {margin-left: 3.2em} div.lisp {margin-left: 3.2em} div.smalldisplay {margin-left: 3.2em} div.smallexample {margin-left: 3.2em} div.smalllisp {margin-left: 3.2em} kbd {font-style: oblique} pre.display {font-family: inherit} pre.format {font-family: inherit} pre.menu-comment {font-family: serif} pre.menu-preformatted {font-family: serif} pre.smalldisplay {font-family: inherit; font-size: smaller} pre.smallexample {font-size: smaller} pre.smallformat {font-family: inherit; font-size: smaller} pre.smalllisp {font-size: smaller} span.nolinebreak {white-space: nowrap} span.roman {font-family: initial; font-weight: normal} span.sansserif {font-family: sans-serif; font-weight: normal} ul.no-bullet {list-style: none} --> </style> </head> <body lang="en"> <a name="Iterators-In-Guile"></a> <div class="header"> <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> </div> <hr> <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> <hr> <div class="header"> <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> </div> </body> </html>