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Inner Product: Difference between revisions
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→Differences between dialects: clarify why ISO IP does not allow for an item-at-a-time algorithm
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(3 4⍴5)+.×1 5⍴6 ⍝ works in NARS2000 or APL\360, not in Dyalog APL</syntaxhighlight> | (3 4⍴5)+.×1 5⍴6 ⍝ works in NARS2000 or APL\360, not in Dyalog APL</syntaxhighlight> | ||
</blockquote> | </blockquote> | ||
The <syntaxhighlight lang=apl>⊃⍤0⊢(↓⍺)∘.(⍺⍺/⍵⍵¨)↓(¯1⌽⍳⍴⍴⍵)⍉⍵</syntaxhighlight> line of IP above can be rewritten as <syntaxhighlight lang=apl>⍺(⍺⍺⌿⍵⍵¨⍤¯1)⍤1 99⊢⍵</syntaxhighlight> which uses the more efficient | The <syntaxhighlight lang=apl>⊃⍤0⊢(↓⍺)∘.(⍺⍺/⍵⍵¨)↓(¯1⌽⍳⍴⍴⍵)⍉⍵</syntaxhighlight> line of IP above can be rewritten as <syntaxhighlight lang=apl>⍺(⍺⍺⌿⍵⍵¨⍤¯1)⍤1 99⊢⍵</syntaxhighlight> which uses the more efficient [[item]]-at-a-time algorithm (rather than row-by-column). The ISO/IEC 13751:2001(E) inner product, conversely, can only be calculated row-by-column, as computing the results one item (of the right argument) at a time relies on each application of the right operand being done between two scalars and producing a scalar result—that is, on the [[Each]] operator being applied to the right operand. | ||
Some implementations extend the inner product by implementing Iverson's monadic variant<ref>[[Ken Iverson|K.E. Iverson]]. [https://www.jsoftware.com/papers/satn42.htm Determinant-Like Functions Produced by the Dot Operator.] SHARP APL Technical Note 42. 1982-04-01.</ref>, which takes a single argument and performs the operation of computing the alternant, as modelled by [https://dfns.dyalog.com/n_alt.htm dfns.alt]. | Some implementations extend the inner product by implementing Iverson's monadic variant<ref>[[Ken Iverson|K.E. Iverson]]. [https://www.jsoftware.com/papers/satn42.htm Determinant-Like Functions Produced by the Dot Operator.] SHARP APL Technical Note 42. 1982-04-01.</ref>, which takes a single argument and performs the operation of computing the alternant, as modelled by [https://dfns.dyalog.com/n_alt.htm dfns.alt]. | ||