103 lines
7.9 KiB
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103 lines
7.9 KiB
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<!-- This manual documents Guile version 3.0.10.
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Inc.
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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Permission is granted to copy, distribute and/or modify this document
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<title>Weak hash tables (Guile Reference Manual)</title>
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Weak-References.html" rel="up" title="Weak References">
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<link href="Weak-vectors.html" rel="next" title="Weak vectors">
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<div class="subsubsection-level-extent" id="Weak-hash-tables">
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<div class="nav-panel">
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<p>
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Next: <a href="Weak-vectors.html" accesskey="n" rel="next">Weak vectors</a>, Up: <a href="Weak-References.html" accesskey="u" rel="up">Weak References</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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<hr>
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<h4 class="subsubsection" id="Weak-hash-tables-1"><span>6.17.3.1 Weak hash tables<a class="copiable-link" href="#Weak-hash-tables-1"> ¶</a></span></h4>
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<dl class="first-deffn">
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<dt class="deffn" id="index-make_002dweak_002dkey_002dhash_002dtable"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">make-weak-key-hash-table</strong> <var class="def-var-arguments">[size]</var><a class="copiable-link" href="#index-make_002dweak_002dkey_002dhash_002dtable"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-make_002dweak_002dvalue_002dhash_002dtable"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">make-weak-value-hash-table</strong> <var class="def-var-arguments">[size]</var><a class="copiable-link" href="#index-make_002dweak_002dvalue_002dhash_002dtable"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-make_002ddoubly_002dweak_002dhash_002dtable"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">make-doubly-weak-hash-table</strong> <var class="def-var-arguments">[size]</var><a class="copiable-link" href="#index-make_002ddoubly_002dweak_002dhash_002dtable"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fmake_005fweak_005fkey_005fhash_005ftable"><span class="category-def">C Function: </span><span><strong class="def-name">scm_make_weak_key_hash_table</strong> <var class="def-var-arguments">(size)</var><a class="copiable-link" href="#index-scm_005fmake_005fweak_005fkey_005fhash_005ftable"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fmake_005fweak_005fvalue_005fhash_005ftable"><span class="category-def">C Function: </span><span><strong class="def-name">scm_make_weak_value_hash_table</strong> <var class="def-var-arguments">(size)</var><a class="copiable-link" href="#index-scm_005fmake_005fweak_005fvalue_005fhash_005ftable"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fmake_005fdoubly_005fweak_005fhash_005ftable"><span class="category-def">C Function: </span><span><strong class="def-name">scm_make_doubly_weak_hash_table</strong> <var class="def-var-arguments">(size)</var><a class="copiable-link" href="#index-scm_005fmake_005fdoubly_005fweak_005fhash_005ftable"> ¶</a></span></dt>
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<dd><p>Return a weak hash table with <var class="var">size</var> buckets. As with any
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hash table, choosing a good size for the table requires some
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caution.
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</p>
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<p>You can modify weak hash tables in exactly the same way you would modify
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regular hash tables, with the exception of the routines that act on
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handles. Weak tables have a different implementation behind the scenes
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that doesn’t have handles. see <a class="pxref" href="Hash-Tables.html">Hash Tables</a>, for more on
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<code class="code">hashq-ref</code> et al.
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</p></dd></dl>
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<p>Note that in a weak-key hash table, the reference to the value is
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strong. This means that if the value references the key, even
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indirectly, the key will never be collected, which can lead to a memory
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leak. The reverse is true for weak value tables.
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</p>
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<dl class="first-deffn">
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<dt class="deffn" id="index-weak_002dkey_002dhash_002dtable_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">weak-key-hash-table?</strong> <var class="def-var-arguments">obj</var><a class="copiable-link" href="#index-weak_002dkey_002dhash_002dtable_003f"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-weak_002dvalue_002dhash_002dtable_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">weak-value-hash-table?</strong> <var class="def-var-arguments">obj</var><a class="copiable-link" href="#index-weak_002dvalue_002dhash_002dtable_003f"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-doubly_002dweak_002dhash_002dtable_003f"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">doubly-weak-hash-table?</strong> <var class="def-var-arguments">obj</var><a class="copiable-link" href="#index-doubly_002dweak_002dhash_002dtable_003f"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fweak_005fkey_005fhash_005ftable_005fp"><span class="category-def">C Function: </span><span><strong class="def-name">scm_weak_key_hash_table_p</strong> <var class="def-var-arguments">(obj)</var><a class="copiable-link" href="#index-scm_005fweak_005fkey_005fhash_005ftable_005fp"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fweak_005fvalue_005fhash_005ftable_005fp"><span class="category-def">C Function: </span><span><strong class="def-name">scm_weak_value_hash_table_p</strong> <var class="def-var-arguments">(obj)</var><a class="copiable-link" href="#index-scm_005fweak_005fvalue_005fhash_005ftable_005fp"> ¶</a></span></dt>
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<dt class="deffnx def-cmd-deffn" id="index-scm_005fdoubly_005fweak_005fhash_005ftable_005fp"><span class="category-def">C Function: </span><span><strong class="def-name">scm_doubly_weak_hash_table_p</strong> <var class="def-var-arguments">(obj)</var><a class="copiable-link" href="#index-scm_005fdoubly_005fweak_005fhash_005ftable_005fp"> ¶</a></span></dt>
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<dd><p>Return <code class="code">#t</code> if <var class="var">obj</var> is the specified weak hash
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table. Note that a doubly weak hash table is neither a weak key
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nor a weak value hash table.
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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="Weak-vectors.html">Weak vectors</a>, Up: <a href="Weak-References.html">Weak References</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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