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165 lines
9.3 KiB
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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-43 Searching (Guile Reference Manual)</title>
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<div class="subsubsection-level-extent" id="SRFI_002d43-Searching">
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<p>
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Next: <a href="SRFI_002d43-Mutators.html" accesskey="n" rel="next">SRFI-43 Mutators</a>, Previous: <a href="SRFI_002d43-Iteration.html" accesskey="p" rel="prev">SRFI-43 Iteration</a>, Up: <a href="SRFI_002d43.html" accesskey="u" rel="up">SRFI-43 - Vector Library</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="SRFI_002d43-Searching-1"><span>7.5.30.5 SRFI-43 Searching<a class="copiable-link" href="#SRFI_002d43-Searching-1"> ¶</a></span></h4>
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<dl class="first-deffn">
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<dt class="deffn" id="index-vector_002dindex"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">vector-index</strong> <var class="def-var-arguments">pred? vec1 vec2 …</var><a class="copiable-link" href="#index-vector_002dindex"> ¶</a></span></dt>
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<dd><p>Find and return the index of the first elements in <var class="var">vec1</var> <var class="var">vec2</var>
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… that satisfy <var class="var">pred?</var>. If no matching element is found by
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the end of the shortest vector, return <code class="code">#f</code>.
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</p>
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<div class="example">
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<pre class="example-preformatted">(vector-index even? '#(3 1 4 1 5 9))
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⇒ 2
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(vector-index < '#(3 1 4 1 5 9 2 5 6) '#(2 7 1 8 2))
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⇒ 1
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(vector-index = '#(3 1 4 1 5 9 2 5 6) '#(2 7 1 8 2))
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⇒ #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-vector_002dindex_002dright"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">vector-index-right</strong> <var class="def-var-arguments">pred? vec1 vec2 …</var><a class="copiable-link" href="#index-vector_002dindex_002dright"> ¶</a></span></dt>
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<dd><p>Like <code class="code">vector-index</code>, but it searches right-to-left, rather than
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left-to-right. Note that the SRFI 43 specification requires that all
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the vectors must have the same length, but both the SRFI 43 reference
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implementation and Guile’s implementation allow vectors with unequal
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lengths, and start searching from the last index of the shortest vector.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-vector_002dskip"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">vector-skip</strong> <var class="def-var-arguments">pred? vec1 vec2 …</var><a class="copiable-link" href="#index-vector_002dskip"> ¶</a></span></dt>
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<dd><p>Find and return the index of the first elements in <var class="var">vec1</var> <var class="var">vec2</var>
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… that do not satisfy <var class="var">pred?</var>. If no matching element is
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found by the end of the shortest vector, return <code class="code">#f</code>. Equivalent
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to <code class="code">vector-index</code> but with the predicate inverted.
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</p>
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<div class="example">
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<pre class="example-preformatted">(vector-skip number? '#(1 2 a b 3 4 c d)) ⇒ 2
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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-vector_002dskip_002dright"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">vector-skip-right</strong> <var class="def-var-arguments">pred? vec1 vec2 …</var><a class="copiable-link" href="#index-vector_002dskip_002dright"> ¶</a></span></dt>
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<dd><p>Like <code class="code">vector-skip</code>, but it searches for a non-matching element
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right-to-left, rather than left-to-right. Note that the SRFI 43
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specification requires that all the vectors must have the same length,
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but both the SRFI 43 reference implementation and Guile’s implementation
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allow vectors with unequal lengths, and start searching from the last
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index of the shortest vector.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-vector_002dbinary_002dsearch"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">vector-binary-search</strong> <var class="def-var-arguments">vec value cmp [start [end]]</var><a class="copiable-link" href="#index-vector_002dbinary_002dsearch"> ¶</a></span></dt>
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<dd><p>Find and return an index of <var class="var">vec</var> between <var class="var">start</var> and <var class="var">end</var>
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whose value is <var class="var">value</var> using a binary search. If no matching
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element is found, return <code class="code">#f</code>. The default <var class="var">start</var> is 0 and
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the default <var class="var">end</var> is the length of <var class="var">vec</var>.
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</p>
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<p><var class="var">cmp</var> must be a procedure of two arguments such that <code class="code">(cmp a
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b)</code> returns a negative integer if <em class="math">a < b</em>, a positive integer if
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<em class="math">a > b</em>, or zero if <em class="math">a = b</em>. The elements of <var class="var">vec</var> must
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be sorted in non-decreasing order according to <var class="var">cmp</var>.
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</p>
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<p>Note that SRFI 43 does not document the <var class="var">start</var> and <var class="var">end</var>
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arguments, but both its reference implementation and Guile’s
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implementation support them.
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</p>
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<div class="example">
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<pre class="example-preformatted">(define (char-cmp c1 c2)
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(cond ((char<? c1 c2) -1)
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((char>? c1 c2) 1)
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(else 0)))
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(vector-binary-search '#(#\a #\b #\c #\d #\e #\f #\g #\h)
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#\g
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char-cmp)
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⇒ 6
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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-vector_002dany"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">vector-any</strong> <var class="def-var-arguments">pred? vec1 vec2 …</var><a class="copiable-link" href="#index-vector_002dany"> ¶</a></span></dt>
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<dd><p>Find the first parallel set of elements from <var class="var">vec1</var> <var class="var">vec2</var>
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… for which <var class="var">pred?</var> returns a true value. If such a parallel
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set of elements exists, <code class="code">vector-any</code> returns the value that
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<var class="var">pred?</var> returned for that set of elements. The iteration is
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strictly left-to-right.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-vector_002devery"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">vector-every</strong> <var class="def-var-arguments">pred? vec1 vec2 …</var><a class="copiable-link" href="#index-vector_002devery"> ¶</a></span></dt>
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<dd><p>If, for every index i between 0 and the length of the shortest vector
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argument, the set of elements <code class="code">(vector-ref vec1 i)</code>
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<code class="code">(vector-ref vec2 i)</code> … satisfies <var class="var">pred?</var>,
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<code class="code">vector-every</code> returns the value that <var class="var">pred?</var> returned for the
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last set of elements, at the last index of the shortest vector.
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Otherwise it returns <code class="code">#f</code>. The iteration is strictly
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left-to-right.
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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_002d43-Mutators.html">SRFI-43 Mutators</a>, Previous: <a href="SRFI_002d43-Iteration.html">SRFI-43 Iteration</a>, Up: <a href="SRFI_002d43.html">SRFI-43 - Vector Library</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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