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155 lines
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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<title>SRFI-37 (Guile Reference Manual)</title>
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<div class="subsection-level-extent" id="SRFI_002d37">
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<p>
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Next: <a href="SRFI_002d38.html" accesskey="n" rel="next">SRFI-38 - External Representation for Data With Shared Structure</a>, Previous: <a href="SRFI_002d35.html" accesskey="p" rel="prev">SRFI-35 - Conditions</a>, Up: <a href="SRFI-Support.html" accesskey="u" rel="up">SRFI Support Modules</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
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<h4 class="subsection" id="SRFI_002d37-_002d-args_002dfold"><span>7.5.25 SRFI-37 - args-fold<a class="copiable-link" href="#SRFI_002d37-_002d-args_002dfold"> ¶</a></span></h4>
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<a class="index-entry-id" id="index-SRFI_002d37"></a>
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<p>This is a processor for GNU <code class="code">getopt_long</code>-style program
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arguments. It provides an alternative, less declarative interface
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than <code class="code">getopt-long</code> in <code class="code">(ice-9 getopt-long)</code>
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(see <a class="pxref" href="getopt_002dlong.html">The (ice-9 getopt-long) Module</a>). Unlike
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<code class="code">getopt-long</code>, it supports repeated options and any number of
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short and long names per option. Access it with:
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(use-modules (srfi srfi-37))
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</pre></div>
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<p><abbr class="acronym">SRFI</abbr>-37 principally provides an <code class="code">option</code> type and the
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<code class="code">args-fold</code> function. To use the library, create a set of
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options with <code class="code">option</code> and use it as a specification for invoking
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<code class="code">args-fold</code>.
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</p>
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<p>Here is an example of a simple argument processor for the typical
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‘<samp class="samp">--version</samp>’ and ‘<samp class="samp">--help</samp>’ options, which returns a backwards
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list of files given on the command line:
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(args-fold (cdr (program-arguments))
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(let ((display-and-exit-proc
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(lambda (msg)
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(lambda (opt name arg loads)
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(display msg) (quit)))))
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(list (option '(#\v "version") #f #f
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(display-and-exit-proc "Foo version 42.0\n"))
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(option '(#\h "help") #f #f
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(display-and-exit-proc
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"Usage: foo scheme-file ..."))))
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(lambda (opt name arg loads)
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(error "Unrecognized option `~A'" name))
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(lambda (op loads) (cons op loads))
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'())
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</pre></div>
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<dl class="first-deffn">
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<dt class="deffn" id="index-option-1"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">option</strong> <var class="def-var-arguments">names required-arg? optional-arg? processor</var><a class="copiable-link" href="#index-option-1"> ¶</a></span></dt>
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<dd><p>Return an object that specifies a single kind of program option.
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</p>
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<p><var class="var">names</var> is a list of command-line option names, and should consist of
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characters for traditional <code class="code">getopt</code> short options and strings for
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<code class="code">getopt_long</code>-style long options.
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</p>
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<p><var class="var">required-arg?</var> and <var class="var">optional-arg?</var> are mutually exclusive;
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one or both must be <code class="code">#f</code>. If <var class="var">required-arg?</var>, the option
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must be followed by an argument on the command line, such as
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‘<samp class="samp">--opt=value</samp>’ for long options, or an error will be signaled.
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If <var class="var">optional-arg?</var>, an argument will be taken if available.
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</p>
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<p><var class="var">processor</var> is a procedure that takes at least 3 arguments, called
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when <code class="code">args-fold</code> encounters the option: the containing option
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object, the name used on the command line, and the argument given for
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the option (or <code class="code">#f</code> if none). The rest of the arguments are
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<code class="code">args-fold</code> “seeds”, and the <var class="var">processor</var> should return
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seeds as well.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-option_002dnames"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">option-names</strong> <var class="def-var-arguments">opt</var><a class="copiable-link" href="#index-option_002dnames"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-option_002drequired_002darg_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">option-required-arg?</strong> <var class="def-var-arguments">opt</var><a class="copiable-link" href="#index-option_002drequired_002darg_003f"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-option_002doptional_002darg_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">option-optional-arg?</strong> <var class="def-var-arguments">opt</var><a class="copiable-link" href="#index-option_002doptional_002darg_003f"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-option_002dprocessor"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">option-processor</strong> <var class="def-var-arguments">opt</var><a class="copiable-link" href="#index-option_002dprocessor"> ¶</a></span></dt>
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<dd><p>Return the specified field of <var class="var">opt</var>, an option object, as
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described above for <code class="code">option</code>.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-args_002dfold"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">args-fold</strong> <var class="def-var-arguments">args options unrecognized-option-proc operand-proc seed …</var><a class="copiable-link" href="#index-args_002dfold"> ¶</a></span></dt>
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<dd><p>Process <var class="var">args</var>, a list of program arguments such as that returned by
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<code class="code">(cdr (program-arguments))</code>, in order against <var class="var">options</var>, a list
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of option objects as described above. All functions called take the
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“seeds”, or the last multiple-values as multiple arguments, starting
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with <var class="var">seed</var> …, and must return the new seeds. Return the
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final seeds.
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</p>
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<p>Call <code class="code">unrecognized-option-proc</code>, which is like an option object’s
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processor, for any options not found in <var class="var">options</var>.
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</p>
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<p>Call <code class="code">operand-proc</code> with any items on the command line that are
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not named options. This includes arguments after ‘<samp class="samp">--</samp>’. It is
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called with the argument in question, as well as the seeds.
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</p></dd></dl>
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</div>
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<hr>
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<div class="nav-panel">
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<p>
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Next: <a href="SRFI_002d38.html">SRFI-38 - External Representation for Data With Shared Structure</a>, Previous: <a href="SRFI_002d35.html">SRFI-35 - Conditions</a>, Up: <a href="SRFI-Support.html">SRFI Support Modules</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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