Operators for recursion

Abstract

Recursion is frequently used in functional programming languages. In LISP, it is the primary means of traversing data structures, and, along with COND, is instrumental in controlling program flow. In APL2, the generalization of arrays to include arrays of arrays encourages the use of recursion. This usage is enhanced by the generalization of, and extensions to, operators. In particular, the ability to define operators allows us to create operators which simplify the coding of recursive logic. This paper studies the use of operators to provide program control for solutions to problems which involve recursion. For the most part, iteration on the elements of a list is used to replace recursive function calls. The program control methods used in this paper are introduced in a companion paper, Operators for Program Control (EusebiC31). The reader is encouraged to read that paper first.