On the question of fill

ABSTRACT

Two unrelated areas of APL have become the basis for the notion of prototype in some groups of extensions to APL. One of these areas, which arises when new operators like Rank, or its special case Each, are considered, is the question of empty frames: what result to return when an expression specifies, roughly, that a function is to be applied to "no data". The second is: what elements should be used to "fill up" the result of expressions like A↑B or B\D, in which some elements of the result are to be taken from the right argument, but other elements may be needed to make a result of the proper shape.The paper "An Operator Calculus" [1] shows how the question of empty frames may be resolved, using a part of functions, without introducing the question of type, let alone that of prototypes.This note discusses an approach to the second question, in the context (and with the notation) of the line of APL development espoused by Iverson in "Rationalized APL" and related papers [2].

REFERENCES

• 1: Kenneth E. Iverson , Roland Pesch , J. Henri Schueler, An operator calculus, Proceedings of the international conference on APL, p.213-218, June 11-15, 1984, Finland
• 2: Kenneth E. Iverson, APL syntax and semantics, Proceedings of the international conference on APL, p.223-231, April 10-13, 1983, Washington, D.C., United States
• 3: [3] For example, as described in the APL2 Language Manual, SB21-3015-0, IBM (1982).
• 4: [4] E. E. McDonnell. Mask and mesh, Minnowbrook Workshop (1980). Also: K. E. Iverson. Operators, TOPLAS 1 2 (1979).

INDEX TERMS

Primary Classification:
  D. Software
  D.3 PROGRAMMING LANGUAGES

General Terms:
Design, Languages, Performance, Theory