Replicate each, anyone?

ABSTRACT

In both the IPSA and APL2/NARS extensions of APL, the SLASH symbol always represents an operator. Some new users of APL2, having been taught in the past that SLASH is an ambiguous symbol which is a dyadic function when it immediately follows data, find that the result when SLASH occurs between data and another operator is incompatible with that interpretation. The situation did not arise in APL1 because derived functions could not be operands. The classification of SLASH as an operator can be traced to the description given in the book. A Programming Language, from which APL ultimately derives. It was done so that the closely related MASK operation could be specified with the same symbol. In this paper the syntactic differences between dyadic functions and aonadic operators with data operands are explicated using the APL2 concept of syntactic binding. Two straightforward language extensions are considered based on the notions of a depth property, which APL2 shares with STSC's NARS, and pairwise evaluation, which derives from syntactic binding. Together they allow either dyadic functions or monadic operators with data operands to be executed in three structural contexts, which, in the cases of REPLICATE and EXPAND, can be loosely described as the same mask for each of several arrays, a separate mask for each array, and the same array for each of several masks.

REFERENCES

• 1: J. Philip Benkard, Structural experiments with arrays of functions, ACM SIGAPL APL Quote Quad, v.15 n.4, p.166-172, May 12, 1985
• 2: Kenneth E. Iverson, A Programming Language., John Wiley & Sons, 1962
• 3: J. Philip Benkard, Syntactic experiments with arrays of functions and operators, ACM SIGAPL APL Quote Quad, v.14 n.4, p.41-51, June 1984
• 4: Kenneth E. Iverson, The role of operators in APL, ACM SIGAPL APL Quote Quad, v.9 n.4, p.128-133, June 1979
• 5: James A. Brown, Function assignment and arrays of functions, ACM SIGAPL APL Quote Quad, v.14 n.4, p.81-84, June 1984
• 6: J. D. Bunda , J. A. Gerth, APL two by two-syntax analysis by pairwise reduction, ACM SIGAPL APL Quote Quad, v.14 n.4, p.85-94, June 1984
• 7: J. Philip Benkard, Valence and precedence in APL extensions, ACM SIGAPL APL Quote Quad, v.13 n.3, p.233-242, March 1983
• 8: IBM Corporationr APL2 Language Manual, Order : SH130-9237.
• 9: J. Philip Benkard, Analysis of function applications in deep arrays, ACM SIGAPL APL Quote Quad, v.16 n.4, p.202-210, 1986
• 10: David J. Landaeta, A notation for manipulating arrays of operations, ACM SIGAPL APL Quote Quad, v.16 n.4, p.21-29, 1986

INDEX TERMS

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

          Nouns: APL
      D.3.3 Language Constructs and Features
          Subjects: Procedures, functions, and subroutines

General Terms:
Design, Languages