APL (programming Language) - Glossary

Glossary

Some words used in APL literature have meanings that differ from those in both mathematics and the generality of computer science.

Term	Description
function	operation or mapping that takes zero, one (right) or two (left & right) array valued arguments and may return an array valued result. A function may be:
	Primitive - built-in and represented by a single glyph;
	Defined - as a named and ordered collection of program statements;
	Derived - as a combination of an operator with its arguments.
array	data valued object of zero or more orthogonal dimensions in row-major order in which each item is a primitive scalar datum or another array.
niladic	not taking or requiring any arguments,
monadic	requiring only one argument; on the right for a function, on the left for an operator, unary
dyadic	requiring both a left and a right argument, binary
ambivalent or nomadic	capable of use in a monadic or dyadic context, permitting its left argument to be elided
operator	operation or mapping that takes one (left) or two (left & right) function or array valued arguments (operands) and derives a function. An operator may be:
	Primitive - built-in and represented by a single glyph;
	Defined - as a named and ordered collection of program statements.