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Direct definition (operator): Difference between revisions
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Text replacement - "Direct definition (Iverson)" to "Direct definition (notation)"
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{{Built-in|Direct definition|∇}}, in [[NARS]], is a [[primitive]] [[dyadic operator]] that defines an [[anonymous function]] based on source [[string]]s. Its left operand is the source for the function's [[dyadic]] case and the right is the source for the [[monadic]] case. One of these operands may be replaced with a [[Jot]] (using this operator as an operand as with [[Outer Product]]) to indicate an undefined case and create a strictly monadic or dyadic function. | {{Built-in|Direct definition|∇}}, in [[NARS]], is a [[primitive]] [[dyadic operator]] that defines an [[anonymous function]] based on source [[string]]s. Its left operand is the source for the function's [[dyadic]] case and the right is the source for the [[monadic]] case. One of these operands may be replaced with a [[Jot]] (using this operator as an operand as with [[Outer Product]]) to indicate an undefined case and create a strictly monadic or dyadic function. | ||
The format of a source string is similar to that used in [[Direct definition ( | The format of a source string is similar to that used in [[Direct definition (notation)|Iverson's direct definition]], with several small differences. Multiple expressions can be used if separated by <syntaxhighlight lang=apl inline>⋄</syntaxhighlight>. <syntaxhighlight lang=apl inline>⍺</syntaxhighlight> and <syntaxhighlight lang=apl inline>⍵</syntaxhighlight> indicate the left and right [[argument]]s, and <syntaxhighlight lang=apl inline>_</syntaxhighlight> is added to indicate [[recursion]]. Conditions are still indicated with colons <syntaxhighlight lang=apl inline>:</syntaxhighlight>, but the mechanism is extended: rather than a boolean condition placed between false and true cases, it's placed first, and returns a scalar or vector of natural numbers. Each number indicates one of the following groups of statements (separated by further <syntaxhighlight lang=apl inline>:</syntaxhighlight>s and numbered starting at 0), and these groups will then be evaluated, with the result of the last evaluated expression returned from the function as a whole. | ||
== External links == | == External links == | ||