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Index Of - Revision history
2024-03-28T18:42:25Z
Revision history for this page on the wiki
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Adám Brudzewsky: Text replacement - "</source>" to "</syntaxhighlight>"
2022-09-10T21:35:09Z
<p>Text replacement - "</source>" to "</syntaxhighlight>"</p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 21:35, 10 September 2022</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:''This page is about lookups. See [[Indexing]], [[Indices]], [[Index Generator]], and [[Interval Index]] for other operations named after indices.''</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:''This page is about lookups. See [[Indexing]], [[Indices]], [[Index Generator]], and [[Interval Index]] for other operations named after indices.''</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>{{Built-in|Index Of|⍳}} is a [[dyadic]] [[primitive function]] which returns an array of [[index|indices]] where each item in the right [[argument]] appears in the left argument. If some item is not found, the corresponding index returned is one higher than the last index of the left argument. Index Of shares its [[glyph]] <syntaxhighlight lang=apl inline>⍳</<del style="font-weight: bold; text-decoration: none;">source</del>> with the monadic primitive function [[Index Generator]].</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>{{Built-in|Index Of|⍳}} is a [[dyadic]] [[primitive function]] which returns an array of [[index|indices]] where each item in the right [[argument]] appears in the left argument. If some item is not found, the corresponding index returned is one higher than the last index of the left argument. Index Of shares its [[glyph]] <syntaxhighlight lang=apl inline>⍳</<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>> with the monadic primitive function [[Index Generator]].</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Examples ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Examples ==</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>1 2 3 4</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>1 2 3 4</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div></<del style="font-weight: bold; text-decoration: none;">source</del>></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div></<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Both arguments can be [[nested array|nested arrays]]. Each item of the right argument is compared to that of the left argument via [[match|exact match]].</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Both arguments can be [[nested array|nested arrays]]. Each item of the right argument is compared to that of the left argument via [[match|exact match]].</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> 'CAT' 'DOG' 'MOUSE'⍳'DOG' 'BIRD'</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> 'CAT' 'DOG' 'MOUSE'⍳'DOG' 'BIRD'</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>2 4</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>2 4</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div></<del style="font-weight: bold; text-decoration: none;">source</del>></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div></<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The behavior on "not found" is useful for selection with fallback (analogous to the [[wikipedia:switch statement|switch statement]] with a default branch in C-like languages). To achieve this, one can use <syntaxhighlight lang=apl inline>Z[X⍳Y]</<del style="font-weight: bold; text-decoration: none;">source</del>>, where <syntaxhighlight lang=apl inline>Z</<del style="font-weight: bold; text-decoration: none;">source</del>> is one item longer than <syntaxhighlight lang=apl inline>X</<del style="font-weight: bold; text-decoration: none;">source</del>>. The last item of <syntaxhighlight lang=apl inline>Z</<del style="font-weight: bold; text-decoration: none;">source</del>> corresponds to the fallback item. In the example below, L and R are mapped to the values -1 and 1, while anything else is garbage and mapped to the fallback value of 0.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The behavior on "not found" is useful for selection with fallback (analogous to the [[wikipedia:switch statement|switch statement]] with a default branch in C-like languages). To achieve this, one can use <syntaxhighlight lang=apl inline>Z[X⍳Y]</<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>>, where <syntaxhighlight lang=apl inline>Z</<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>> is one item longer than <syntaxhighlight lang=apl inline>X</<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>>. The last item of <syntaxhighlight lang=apl inline>Z</<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>> corresponds to the fallback item. In the example below, L and R are mapped to the values -1 and 1, while anything else is garbage and mapped to the fallback value of 0.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><syntaxhighlight lang=apl></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><syntaxhighlight lang=apl></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> ¯1 1 0['LR'⍳'LLL?!RR*LRzL']</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> ¯1 1 0['LR'⍳'LLL?!RR*LRzL']</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>¯1 ¯1 ¯1 0 0 1 1 0 ¯1 1 0 ¯1</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>¯1 ¯1 ¯1 0 0 1 1 0 ¯1 1 0 ¯1</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div></<del style="font-weight: bold; text-decoration: none;">source</del>></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div></<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Properties ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Properties ==</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Extensions for higher-[[rank]] left argument ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Extensions for higher-[[rank]] left argument ==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Dyalog APL]] (since 14.0) and [[J]] follows the [[leading axis theory]], and compares the [[major cell|major cells]] of X with [[cells]] of Y with the same rank. The resulting shape is <syntaxhighlight lang=apl inline>(1-≢⍴X)↓⍴Y</<del style="font-weight: bold; text-decoration: none;">source</del>>. Dyalog APL requires that the shapes of the cells to be compared be equal <syntaxhighlight lang=apl inline>(1↓⍴X)≡(1-≢⍴X)↑⍴Y</<del style="font-weight: bold; text-decoration: none;">source</del>>; otherwise [[LENGTH ERROR]] is raised. J simply treats them as not found.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Dyalog APL]] (since 14.0) and [[J]] follows the [[leading axis theory]], and compares the [[major cell|major cells]] of X with [[cells]] of Y with the same rank. The resulting shape is <syntaxhighlight lang=apl inline>(1-≢⍴X)↓⍴Y</<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>>. Dyalog APL requires that the shapes of the cells to be compared be equal <syntaxhighlight lang=apl inline>(1↓⍴X)≡(1-≢⍴X)↑⍴Y</<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>>; otherwise [[LENGTH ERROR]] is raised. J simply treats them as not found.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[NARS2000]] simply compares items of X to the items of Y, and returns the nested array of shape of Y where each item indicates a multi-dimensional index in X. The index for not found items is <syntaxhighlight lang=apl inline>⎕IO+⍴X</<del style="font-weight: bold; text-decoration: none;">source</del>>. This also works with [[scalar]] X, though the result (an array filled with empty vectors) is not very meaningful.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[NARS2000]] simply compares items of X to the items of Y, and returns the nested array of shape of Y where each item indicates a multi-dimensional index in X. The index for not found items is <syntaxhighlight lang=apl inline>⎕IO+⍴X</<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>>. This also works with [[scalar]] X, though the result (an array filled with empty vectors) is not very meaningful.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[GNU APL]] follows the convention of NARS2000, with the exception that the index for not found items is an [[empty]] [[vector]] (!) instead of <syntaxhighlight lang=apl inline>⎕IO+⍴X</<del style="font-weight: bold; text-decoration: none;">source</del>>.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[GNU APL]] follows the convention of NARS2000, with the exception that the index for not found items is an [[empty]] [[vector]] (!) instead of <syntaxhighlight lang=apl inline>⎕IO+⍴X</<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight</ins>>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== External links ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== External links ==</div></td></tr>
</table>
Adám Brudzewsky
https://aplwiki.com/index.php?title=Index_Of&diff=9115&oldid=prev
Adám Brudzewsky: Text replacement - "<source" to "<syntaxhighlight"
2022-09-10T20:55:27Z
<p>Text replacement - "<source" to "<syntaxhighlight"</p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 20:55, 10 September 2022</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1">Line 1:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:''This page is about lookups. See [[Indexing]], [[Indices]], [[Index Generator]], and [[Interval Index]] for other operations named after indices.''</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:''This page is about lookups. See [[Indexing]], [[Indices]], [[Index Generator]], and [[Interval Index]] for other operations named after indices.''</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>{{Built-in|Index Of|⍳}} is a [[dyadic]] [[primitive function]] which returns an array of [[index|indices]] where each item in the right [[argument]] appears in the left argument. If some item is not found, the corresponding index returned is one higher than the last index of the left argument. Index Of shares its [[glyph]] <<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl inline>⍳</source> with the monadic primitive function [[Index Generator]].</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>{{Built-in|Index Of|⍳}} is a [[dyadic]] [[primitive function]] which returns an array of [[index|indices]] where each item in the right [[argument]] appears in the left argument. If some item is not found, the corresponding index returned is one higher than the last index of the left argument. Index Of shares its [[glyph]] <<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl inline>⍳</source> with the monadic primitive function [[Index Generator]].</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Examples ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Examples ==</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The right argument can have any [[shape]], but the left argument is usually restricted to a [[vector]]. The result is a [[simple]] integer array with the shape of the right argument, and each cell indicates at which index the corresponding item is found (or not found at all) in the left argument.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The right argument can have any [[shape]], but the left argument is usually restricted to a [[vector]]. The result is a [[simple]] integer array with the shape of the right argument, and each cell indicates at which index the corresponding item is found (or not found at all) in the left argument.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> ⎕←x←2 3 4⍴'ABCDZ'</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> ⎕←x←2 3 4⍴'ABCDZ'</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>ABCD</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>ABCD</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l27">Line 27:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Both arguments can be [[nested array|nested arrays]]. Each item of the right argument is compared to that of the left argument via [[match|exact match]].</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Both arguments can be [[nested array|nested arrays]]. Each item of the right argument is compared to that of the left argument via [[match|exact match]].</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> 'CAT' 'DOG' 'MOUSE'⍳'DOG' 'BIRD'</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> 'CAT' 'DOG' 'MOUSE'⍳'DOG' 'BIRD'</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>2 4</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>2 4</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div></source></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div></source></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The behavior on "not found" is useful for selection with fallback (analogous to the [[wikipedia:switch statement|switch statement]] with a default branch in C-like languages). To achieve this, one can use <<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl inline>Z[X⍳Y]</source>, where <<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl inline>Z</source> is one item longer than <<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl inline>X</source>. The last item of <<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl inline>Z</source> corresponds to the fallback item. In the example below, L and R are mapped to the values -1 and 1, while anything else is garbage and mapped to the fallback value of 0.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The behavior on "not found" is useful for selection with fallback (analogous to the [[wikipedia:switch statement|switch statement]] with a default branch in C-like languages). To achieve this, one can use <<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl inline>Z[X⍳Y]</source>, where <<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl inline>Z</source> is one item longer than <<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl inline>X</source>. The last item of <<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl inline>Z</source> corresponds to the fallback item. In the example below, L and R are mapped to the values -1 and 1, while anything else is garbage and mapped to the fallback value of 0.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> ¯1 1 0['LR'⍳'LLL?!RR*LRzL']</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> ¯1 1 0['LR'⍳'LLL?!RR*LRzL']</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>¯1 ¯1 ¯1 0 0 1 1 0 ¯1 1 0 ¯1</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>¯1 ¯1 ¯1 0 0 1 1 0 ¯1 1 0 ¯1</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l45">Line 45:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Extensions for higher-[[rank]] left argument ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Extensions for higher-[[rank]] left argument ==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Dyalog APL]] (since 14.0) and [[J]] follows the [[leading axis theory]], and compares the [[major cell|major cells]] of X with [[cells]] of Y with the same rank. The resulting shape is <<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl inline>(1-≢⍴X)↓⍴Y</source>. Dyalog APL requires that the shapes of the cells to be compared be equal <<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl inline>(1↓⍴X)≡(1-≢⍴X)↑⍴Y</source>; otherwise [[LENGTH ERROR]] is raised. J simply treats them as not found.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Dyalog APL]] (since 14.0) and [[J]] follows the [[leading axis theory]], and compares the [[major cell|major cells]] of X with [[cells]] of Y with the same rank. The resulting shape is <<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl inline>(1-≢⍴X)↓⍴Y</source>. Dyalog APL requires that the shapes of the cells to be compared be equal <<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl inline>(1↓⍴X)≡(1-≢⍴X)↑⍴Y</source>; otherwise [[LENGTH ERROR]] is raised. J simply treats them as not found.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[NARS2000]] simply compares items of X to the items of Y, and returns the nested array of shape of Y where each item indicates a multi-dimensional index in X. The index for not found items is <<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl inline>⎕IO+⍴X</source>. This also works with [[scalar]] X, though the result (an array filled with empty vectors) is not very meaningful.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[NARS2000]] simply compares items of X to the items of Y, and returns the nested array of shape of Y where each item indicates a multi-dimensional index in X. The index for not found items is <<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl inline>⎕IO+⍴X</source>. This also works with [[scalar]] X, though the result (an array filled with empty vectors) is not very meaningful.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[GNU APL]] follows the convention of NARS2000, with the exception that the index for not found items is an [[empty]] [[vector]] (!) instead of <<del style="font-weight: bold; text-decoration: none;">source </del>lang=apl inline>⎕IO+⍴X</source>.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[GNU APL]] follows the convention of NARS2000, with the exception that the index for not found items is an [[empty]] [[vector]] (!) instead of <<ins style="font-weight: bold; text-decoration: none;">syntaxhighlight </ins>lang=apl inline>⎕IO+⍴X</source>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== External links ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== External links ==</div></td></tr>
</table>
Adám Brudzewsky
https://aplwiki.com/index.php?title=Index_Of&diff=7105&oldid=prev
Marshall: /* Documentation */ BQN link
2021-07-17T02:51:30Z
<p><span dir="auto"><span class="autocomment">Documentation: </span> BQN link</span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 02:51, 17 July 2021</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [http://microapl.com/apl_help/ch_020_020_160.htm APLX]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [http://microapl.com/apl_help/ch_020_020_160.htm APLX]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* J [https://www.jsoftware.com/help/dictionary/didot.htm Dictionary], [https://code.jsoftware.com/wiki/Vocabulary/idot#dyadic Nuvoc]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* J [https://www.jsoftware.com/help/dictionary/didot.htm Dictionary], [https://code.jsoftware.com/wiki/Vocabulary/idot#dyadic Nuvoc]</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">* [https://mlochbaum.github.io/BQN/doc/search.html#index-of BQN]</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{APL built-ins}}[[Category:Primitive functions]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{APL built-ins}}[[Category:Primitive functions]]</div></td></tr>
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Marshall
https://aplwiki.com/index.php?title=Index_Of&diff=5546&oldid=prev
Adám Brudzewsky at 05:34, 19 October 2020
2020-10-19T05:34:12Z
<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 05:34, 19 October 2020</td>
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<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">:''This page is about lookups. See [[Indexing]], [[Indices]], [[Index Generator]], and [[Interval Index]] for other operations named after indices.''</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{Built-in|Index Of|⍳}} is a [[dyadic]] [[primitive function]] which returns an array of [[index|indices]] where each item in the right [[argument]] appears in the left argument. If some item is not found, the corresponding index returned is one higher than the last index of the left argument. Index Of shares its [[glyph]] <source lang=apl inline>⍳</source> with the monadic primitive function [[Index Generator]].</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{Built-in|Index Of|⍳}} is a [[dyadic]] [[primitive function]] which returns an array of [[index|indices]] where each item in the right [[argument]] appears in the left argument. If some item is not found, the corresponding index returned is one higher than the last index of the left argument. Index Of shares its [[glyph]] <source lang=apl inline>⍳</source> with the monadic primitive function [[Index Generator]].</div></td></tr>
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Adám Brudzewsky
https://aplwiki.com/index.php?title=Index_Of&diff=5148&oldid=prev
Adám Brudzewsky: Text replacement - "http://help.dyalog.com" to "https://help.dyalog.com"
2020-07-14T14:29:46Z
<p>Text replacement - "http://help.dyalog.com" to "https://help.dyalog.com"</p>
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<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>* [<del style="font-weight: bold; text-decoration: none;">http</del>://help.dyalog.com/latest/#Language/Primitive%20Functions/Index%20Of.htm Dyalog]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>* [<ins style="font-weight: bold; text-decoration: none;">https</ins>://help.dyalog.com/latest/#Language/Primitive%20Functions/Index%20Of.htm Dyalog]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [http://wiki.nars2000.org/index.php/Index_Of NARS2000]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [http://wiki.nars2000.org/index.php/Index_Of NARS2000]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [http://microapl.com/apl_help/ch_020_020_160.htm APLX]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [http://microapl.com/apl_help/ch_020_020_160.htm APLX]</div></td></tr>
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Adám Brudzewsky
https://aplwiki.com/index.php?title=Index_Of&diff=4764&oldid=prev
Adám Brudzewsky: Text replacement - " ⊢( *[^∘])" to " ⎕←$1"
2020-06-09T05:48:18Z
<p>Text replacement - " ⊢( *[^∘])" to " ⎕←$1"</p>
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Adám Brudzewsky
https://aplwiki.com/index.php?title=Index_Of&diff=4744&oldid=prev
Adám Brudzewsky: /* Extensions for higher-rank left argument */
2020-06-05T10:25:24Z
<p><span dir="auto"><span class="autocomment">Extensions for higher-rank left argument</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[NARS2000]] simply compares items of X to the items of Y, and returns the nested array of shape of Y where each item indicates a multi-dimensional index in X. The index for not found items is <source lang=apl inline>⎕IO+⍴X</source>. This also works with [[scalar]] X, though the result (an array filled with empty vectors) is not very meaningful.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[NARS2000]] simply compares items of X to the items of Y, and returns the nested array of shape of Y where each item indicates a multi-dimensional index in X. The index for not found items is <source lang=apl inline>⎕IO+⍴X</source>. This also works with [[scalar]] X, though the result (an array filled with empty vectors) is not very meaningful.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[GNU APL]] follows the convention of NARS2000, with the exception that the index for not found items is an [[empty]] [[vector]] <del style="font-weight: bold; text-decoration: none;"><source lang=apl </del>(!) instead of <source lang=apl inline>⎕IO+⍴X</source>.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[GNU APL]] follows the convention of NARS2000, with the exception that the index for not found items is an [[empty]] [[vector]] (!) instead of <source lang=apl inline>⎕IO+⍴X</source>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== External links ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== External links ==</div></td></tr>
</table>
Adám Brudzewsky
https://aplwiki.com/index.php?title=Index_Of&diff=4743&oldid=prev
Adám Brudzewsky: GNU
2020-06-05T10:23:37Z
<p>GNU</p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 10:23, 5 June 2020</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[NARS2000]] simply compares items of X to the items of Y, and returns the nested array of shape of Y where each item indicates a multi-dimensional index in X. The index for not found items is <source lang=apl inline>⎕IO+⍴X</source>. This also works with [[scalar]] X, though the result (an array filled with empty vectors) is not very meaningful.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[NARS2000]] simply compares items of X to the items of Y, and returns the nested array of shape of Y where each item indicates a multi-dimensional index in X. The index for not found items is <source lang=apl inline>⎕IO+⍴X</source>. This also works with [[scalar]] X, though the result (an array filled with empty vectors) is not very meaningful.</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[GNU APL]] follows the convention of NARS2000, with the exception that the index for not found items is an [[empty]] [[vector]] <source lang=apl (!) instead of <source lang=apl inline>⎕IO+⍴X</source>.</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== External links ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== External links ==</div></td></tr>
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Adám Brudzewsky
https://aplwiki.com/index.php?title=Index_Of&diff=4725&oldid=prev
Bubbler: Created page with "{{Built-in|Index Of|⍳}} is a dyadic primitive function which returns an array of indices where each item in the right argument appears in the left argu..."
2020-06-05T04:39:59Z
<p>Created page with "{{Built-in|Index Of|⍳}} is a <a href="/wiki/Dyadic" class="mw-redirect" title="Dyadic">dyadic</a> <a href="/wiki/Primitive_function" title="Primitive function">primitive function</a> which returns an array of <a href="/wiki/Index" title="Index">indices</a> where each item in the right <a href="/wiki/Argument" title="Argument">argument</a> appears in the left argu..."</p>
<p><b>New page</b></p><div>{{Built-in|Index Of|⍳}} is a [[dyadic]] [[primitive function]] which returns an array of [[index|indices]] where each item in the right [[argument]] appears in the left argument. If some item is not found, the corresponding index returned is one higher than the last index of the left argument. Index Of shares its [[glyph]] <source lang=apl inline>⍳</source> with the monadic primitive function [[Index Generator]].<br />
<br />
== Examples ==<br />
<br />
The right argument can have any [[shape]], but the left argument is usually restricted to a [[vector]]. The result is a [[simple]] integer array with the shape of the right argument, and each cell indicates at which index the corresponding item is found (or not found at all) in the left argument.<br />
<br />
<source lang=apl><br />
⊢x←2 3 4⍴'ABCDZ'<br />
ABCD<br />
ZABC<br />
DZAB<br />
<br />
CDZA<br />
BCDZ<br />
ABCD<br />
'ABCD'⍳x<br />
1 2 3 4<br />
5 1 2 3<br />
4 5 1 2<br />
<br />
3 4 5 1<br />
2 3 4 5<br />
1 2 3 4<br />
</source><br />
<br />
Both arguments can be [[nested array|nested arrays]]. Each item of the right argument is compared to that of the left argument via [[match|exact match]].<br />
<br />
<source lang=apl><br />
'CAT' 'DOG' 'MOUSE'⍳'DOG' 'BIRD'<br />
2 4<br />
</source><br />
<br />
The behavior on "not found" is useful for selection with fallback (analogous to the [[wikipedia:switch statement|switch statement]] with a default branch in C-like languages). To achieve this, one can use <source lang=apl inline>Z[X⍳Y]</source>, where <source lang=apl inline>Z</source> is one item longer than <source lang=apl inline>X</source>. The last item of <source lang=apl inline>Z</source> corresponds to the fallback item. In the example below, L and R are mapped to the values -1 and 1, while anything else is garbage and mapped to the fallback value of 0.<br />
<br />
<source lang=apl><br />
¯1 1 0['LR'⍳'LLL?!RR*LRzL']<br />
¯1 ¯1 ¯1 0 0 1 1 0 ¯1 1 0 ¯1<br />
</source><br />
<br />
== Properties ==<br />
<br />
The result of Index Of depends on [[index origin]] and [[comparison tolerance]].<br />
<br />
== Extensions for higher-[[rank]] left argument ==<br />
<br />
[[Dyalog APL]] (since 14.0) and [[J]] follows the [[leading axis theory]], and compares the [[major cell|major cells]] of X with [[cells]] of Y with the same rank. The resulting shape is <source lang=apl inline>(1-≢⍴X)↓⍴Y</source>. Dyalog APL requires that the shapes of the cells to be compared be equal <source lang=apl inline>(1↓⍴X)≡(1-≢⍴X)↑⍴Y</source>; otherwise [[LENGTH ERROR]] is raised. J simply treats them as not found.<br />
<br />
[[NARS2000]] simply compares items of X to the items of Y, and returns the nested array of shape of Y where each item indicates a multi-dimensional index in X. The index for not found items is <source lang=apl inline>⎕IO+⍴X</source>. This also works with [[scalar]] X, though the result (an array filled with empty vectors) is not very meaningful.<br />
<br />
== External links ==<br />
=== Tutorials ===<br />
* [https://chat.stackexchange.com/rooms/52405/conversation/lesson-8-apl-functions--#41583854 APL Cultivation]<br />
<br />
=== Documentation ===<br />
<br />
* [http://help.dyalog.com/latest/#Language/Primitive%20Functions/Index%20Of.htm Dyalog]<br />
* [http://wiki.nars2000.org/index.php/Index_Of NARS2000]<br />
* [http://microapl.com/apl_help/ch_020_020_160.htm APLX]<br />
* J [https://www.jsoftware.com/help/dictionary/didot.htm Dictionary], [https://code.jsoftware.com/wiki/Vocabulary/idot#dyadic Nuvoc]<br />
<br />
{{APL built-ins}}[[Category:Primitive functions]]</div>
Bubbler