Function array

A function array, or fnarray, is a value that is conceptually an array of functions. It can be applied to arguments, which applies each function independently and gives an array of results. Several languages that don't ordinarily support placing a function in an array have function arrays as a special construct: Dyalog APL, dzaima/APL, and Nial, which uses the name "atlas".

In dzaima/APL and Nial function arrays are constructed by the vector form of array notation, allowing only rank-1 function arrays. In Dyalog APL they can be produced by taking a member of an array of namespaces that all contain that member, each with its own function value. in the dfns workspace wraps this functionality in an operator.

The FP language features a "function composition" construction that applies like a function array. In the I language, which has first-class functions, lists may be applied to arguments, and apply each element independently, so that a list of functions also behaves like a function array.