APL procedures (user defined operators, functions and token strings)

Abstract

This paper describes some central aspects of an APL implementation on a Hewlett Packard Minicomputer. The development of these ideas led to an elegant, consistent underlying structure for all procedures, where a procedure is defined as a structured sequence of APL expressions, instances of which are niladic functions, ambivalent functions, monadic operators and dyadic operators. Further to this idea, the introduction of two new functions (tokenize and detokenize) and a single hyperoperator (∇) gave rise to the following features; Ability to manipulate functions and operators as APL objects Extended Assignment applied to all APL objects Ability to store preset (or initialized) values into the header of any procedure Make direct use of the (usually restricted) facet of tokenizing and detokenizing in APL to generate token strings, which may be applied by the programmer to form individual variants of □ FX, □ CR and/or ∇ editing. These extensions have been superimposed upon a basic imprint of SHARP APL.