112 lines
7.1 KiB
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112 lines
7.1 KiB
HTML
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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<title>SRFI-69 Accessing table items (Guile Reference Manual)</title>
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<div class="subsubsection-level-extent" id="SRFI_002d69-Accessing-table-items">
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<p>
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Next: <a href="SRFI_002d69-Table-properties.html" accesskey="n" rel="next">Table properties</a>, Previous: <a href="SRFI_002d69-Creating-hash-tables.html" accesskey="p" rel="prev">Creating hash tables</a>, Up: <a href="SRFI_002d69.html" accesskey="u" rel="up">SRFI-69 - Basic hash tables</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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<h4 class="subsubsection" id="Accessing-table-items"><span>7.5.39.2 Accessing table items<a class="copiable-link" href="#Accessing-table-items"> ¶</a></span></h4>
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<dl class="first-deffn">
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<dt class="deffn" id="index-hash_002dtable_002dref"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">hash-table-ref</strong> <var class="def-var-arguments">table key [default-thunk]</var><a class="copiable-link" href="#index-hash_002dtable_002dref"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-hash_002dtable_002dref_002fdefault"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">hash-table-ref/default</strong> <var class="def-var-arguments">table key default</var><a class="copiable-link" href="#index-hash_002dtable_002dref_002fdefault"> ¶</a></span></dt>
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<dd><p>Answer the value associated with <var class="var">key</var> in <var class="var">table</var>. If
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<var class="var">key</var> is not present, answer the result of invoking the thunk
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<var class="var">default-thunk</var>, which signals an error instead by default.
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</p>
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<p><code class="code">hash-table-ref/default</code> is a variant that requires a third
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argument, <var class="var">default</var>, and answers <var class="var">default</var> itself instead of
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invoking it.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-hash_002dtable_002dset_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">hash-table-set!</strong> <var class="def-var-arguments">table key new-value</var><a class="copiable-link" href="#index-hash_002dtable_002dset_0021"> ¶</a></span></dt>
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<dd><p>Set <var class="var">key</var> to <var class="var">new-value</var> in <var class="var">table</var>.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-hash_002dtable_002ddelete_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">hash-table-delete!</strong> <var class="def-var-arguments">table key</var><a class="copiable-link" href="#index-hash_002dtable_002ddelete_0021"> ¶</a></span></dt>
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<dd><p>Remove the association of <var class="var">key</var> in <var class="var">table</var>, if present. If
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absent, do nothing.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-hash_002dtable_002dexists_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">hash-table-exists?</strong> <var class="def-var-arguments">table key</var><a class="copiable-link" href="#index-hash_002dtable_002dexists_003f"> ¶</a></span></dt>
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<dd><p>Answer whether <var class="var">key</var> has an association in <var class="var">table</var>.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-hash_002dtable_002dupdate_0021"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">hash-table-update!</strong> <var class="def-var-arguments">table key modifier [default-thunk]</var><a class="copiable-link" href="#index-hash_002dtable_002dupdate_0021"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-hash_002dtable_002dupdate_0021_002fdefault"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">hash-table-update!/default</strong> <var class="def-var-arguments">table key modifier default</var><a class="copiable-link" href="#index-hash_002dtable_002dupdate_0021_002fdefault"> ¶</a></span></dt>
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<dd><p>Replace <var class="var">key</var>’s associated value in <var class="var">table</var> by invoking
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<var class="var">modifier</var> with one argument, the old value.
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</p>
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<p>If <var class="var">key</var> is not present, and <var class="var">default-thunk</var> is provided,
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invoke it with no arguments to get the “old value” to be passed to
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<var class="var">modifier</var> as above. If <var class="var">default-thunk</var> is not provided in
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such a case, signal an error.
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</p>
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<p><code class="code">hash-table-update!/default</code> is a variant that requires the
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fourth argument, which is used directly as the “old value” rather
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than as a thunk to be invoked to retrieve the “old value”.
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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_002d69-Table-properties.html">Table properties</a>, Previous: <a href="SRFI_002d69-Creating-hash-tables.html">Creating hash tables</a>, Up: <a href="SRFI_002d69.html">SRFI-69 - Basic hash tables</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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