Function-operator overloading: Difference between revisions

In [[APL syntax]], '''function-operator overloading''' (sometimes '''schizophrenia'''<ref>The term ''schizophrenia'' used to be associated with [[wikipedia:split personality|''split personality'']] by the general population but that usage went into decline when it became known as a separate disorder. The term was used for duality of programming language constructs as early 1978, for example in [https://dl.acm.org/doi/10.1145/800025.1198354 the transcript] of [[Alan Perlis]]'s [[HOPL]] I entry on [[wikipedia:ALGOL 58|ALGOL 58]]. The informal usage has lived on in APL circles when referring to the "split personality" exhibited in primitives affected by function-operator overloading.</ref>) is the practice of using a single [[glyph]] for both a [[primitive function]] and a [[primitive operator]], which is then characterised as a '''hybrid''' primitive. Dialects with this feature include [[Dyalog APL]], [[NARS2000]], [[A+]], and [[GNU APL]]. Notably, [[APL2]] and [[APLX]] avoid this issue by always treating [[Replicate]] and [[Expand]] as operators, however, this requires wrapping in a cover function in order to use these as [[operand]]s. [[Most commonly it refers to one of the slash glyphs (such as <source lang=apl inline>/</source> for [[Replicate]] or [[Reduce]], but not <source lang=apl inline>⍉</source> for [[Transpose]]), but [[assignment]] may also be handled in a similar manner because ordinary assignment has the form of a [[dyadic function]] while [[modified assignment]] works like a [[monadic operator]] applied dyadically. It may apply only to the glyphs themselves, or to their values and derivations as well: for example, in [[Dyalog APL]] the assignments <source lang=apl inline>r←/</source> and even <source lang=apl inline>r←/[3]</source> create variables <source lang=apl inline>r</source> which exhibit overloading.