Structured APL: a proposal for block structured control flow in APL

ABSTRACT

APL, although a very powerful language, has failed to gain wide acceptance in part due to its lack of control structures. A proposal is made for introducing structure in APL objects by adding to the items that can be located on the left of the colon (:). These markers show the beginning and ends of blocks of code and allow for selection, iteration, and termination. The set of control structures is shown to be robust by showing their use in the creation of traditional control structures. A method of conversion to ISO APL is also presented.This paper briefly discusses proposals that have been made in the past along with an evaluation of their merits and shortcomings. The paper ends with a discussion of related issues, including elimination of branching, introduction of definition blocks, and lexical scoping in APL. Several areas for continuing work are given.

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INDEX TERMS

Primary Classification:
  D. Software
  D.3 PROGRAMMING LANGUAGES
      D.3.2 Language Classifications

          Nouns: APL

Additional Classification:
  D. Software
  D.2 SOFTWARE ENGINEERING
      D.2.2 Design Tools and Techniques
          Subjects: Structured programming**
  D.3 PROGRAMMING LANGUAGES
      D.3.3 Language Constructs and Features
          Subjects: Procedures, functions, and subroutines

General Terms:
Algorithms, Languages