137 lines
8.7 KiB
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137 lines
8.7 KiB
HTML
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<title>String Predicates (Guile Reference Manual)</title>
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<div class="subsubsection-level-extent" id="String-Predicates">
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<p>
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Next: <a href="String-Constructors.html" accesskey="n" rel="next">String Constructors</a>, Previous: <a href="String-Syntax.html" accesskey="p" rel="prev">String Read Syntax</a>, Up: <a href="Strings.html" accesskey="u" rel="up">Strings</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="subsubsection" id="String-Predicates-1"><span>6.6.5.2 String Predicates<a class="copiable-link" href="#String-Predicates-1"> ¶</a></span></h4>
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<p>The following procedures can be used to check whether a given string
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fulfills some specified property.
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</p>
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<a class="index-entry-id" id="index-string_003f-3"></a>
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<dl class="first-deffn">
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<dt class="deffn" id="index-string_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">string?</strong> <var class="def-var-arguments">obj</var><a class="copiable-link" href="#index-string_003f"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fstring_005fp"><span class="category-def">C Function: </span><span><strong class="def-name">scm_string_p</strong> <var class="def-var-arguments">(obj)</var><a class="copiable-link" href="#index-scm_005fstring_005fp"> ¶</a></span></dt>
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<dd><p>Return <code class="code">#t</code> if <var class="var">obj</var> is a string, else <code class="code">#f</code>.
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</p></dd></dl>
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<dl class="first-deftypefn">
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<dt class="deftypefn" id="index-scm_005fis_005fstring"><span class="category-def">C Function: </span><span><code class="def-type">int</code> <strong class="def-name">scm_is_string</strong> <code class="def-code-arguments">(SCM obj)</code><a class="copiable-link" href="#index-scm_005fis_005fstring"> ¶</a></span></dt>
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<dd><p>Returns <code class="code">1</code> if <var class="var">obj</var> is a string, <code class="code">0</code> otherwise.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-string_002dnull_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">string-null?</strong> <var class="def-var-arguments">str</var><a class="copiable-link" href="#index-string_002dnull_003f"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fstring_005fnull_005fp"><span class="category-def">C Function: </span><span><strong class="def-name">scm_string_null_p</strong> <var class="def-var-arguments">(str)</var><a class="copiable-link" href="#index-scm_005fstring_005fnull_005fp"> ¶</a></span></dt>
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<dd><p>Return <code class="code">#t</code> if <var class="var">str</var>’s length is zero, and
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<code class="code">#f</code> otherwise.
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</p><div class="example lisp">
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<pre class="lisp-preformatted">(string-null? "") ⇒ #t
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y ⇒ "foo"
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(string-null? y) ⇒ #f
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</pre></div>
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</dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-string_002dany"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">string-any</strong> <var class="def-var-arguments">char_pred s [start [end]]</var><a class="copiable-link" href="#index-string_002dany"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fstring_005fany"><span class="category-def">C Function: </span><span><strong class="def-name">scm_string_any</strong> <var class="def-var-arguments">(char_pred, s, start, end)</var><a class="copiable-link" href="#index-scm_005fstring_005fany"> ¶</a></span></dt>
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<dd><p>Check if <var class="var">char_pred</var> is true for any character in string <var class="var">s</var>.
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</p>
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<p><var class="var">char_pred</var> can be a character to check for any equal to that, or
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a character set (see <a class="pxref" href="Character-Sets.html">Character Sets</a>) to check for any in that set,
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or a predicate procedure to call.
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</p>
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<p>For a procedure, calls <code class="code">(<var class="var">char_pred</var> c)</code> are made
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successively on the characters from <var class="var">start</var> to <var class="var">end</var>. If
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<var class="var">char_pred</var> returns true (ie. non-<code class="code">#f</code>), <code class="code">string-any</code>
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stops and that return value is the return from <code class="code">string-any</code>. The
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call on the last character (ie. at <em class="math"><var class="var">end</var>-1</em>), if that
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point is reached, is a tail call.
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</p>
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<p>If there are no characters in <var class="var">s</var> (ie. <var class="var">start</var> equals
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<var class="var">end</var>) then the return is <code class="code">#f</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-string_002devery"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">string-every</strong> <var class="def-var-arguments">char_pred s [start [end]]</var><a class="copiable-link" href="#index-string_002devery"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fstring_005fevery"><span class="category-def">C Function: </span><span><strong class="def-name">scm_string_every</strong> <var class="def-var-arguments">(char_pred, s, start, end)</var><a class="copiable-link" href="#index-scm_005fstring_005fevery"> ¶</a></span></dt>
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<dd><p>Check if <var class="var">char_pred</var> is true for every character in string
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<var class="var">s</var>.
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</p>
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<p><var class="var">char_pred</var> can be a character to check for every character equal
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to that, or a character set (see <a class="pxref" href="Character-Sets.html">Character Sets</a>) to check for
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every character being in that set, or a predicate procedure to call.
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</p>
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<p>For a procedure, calls <code class="code">(<var class="var">char_pred</var> c)</code> are made
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successively on the characters from <var class="var">start</var> to <var class="var">end</var>. If
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<var class="var">char_pred</var> returns <code class="code">#f</code>, <code class="code">string-every</code> stops and
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returns <code class="code">#f</code>. The call on the last character (ie. at
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<em class="math"><var class="var">end</var>-1</em>), if that point is reached, is a tail call and the
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return from that call is the return from <code class="code">string-every</code>.
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</p>
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<p>If there are no characters in <var class="var">s</var> (ie. <var class="var">start</var> equals
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<var class="var">end</var>) then the return is <code class="code">#t</code>.
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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="String-Constructors.html">String Constructors</a>, Previous: <a href="String-Syntax.html">String Read Syntax</a>, Up: <a href="Strings.html">Strings</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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</html>
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