Functional form

In programming and mathematics, a functional form is an operator or function that can either be applied to other operators (i.e. one or more of its operands or arguments are itself operators) or yield operators as result, or both. It is, thus, essentially the same as a higher-order function, although the syntax may be more reminiscent of (pre-, post-, or infix) operators applied to operands, rather than function application in the lambda calculus tradition. Examples of functional forms are function composition, construction, and apply-to-all, but there are numerous others.