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ABSTRACT

A barrier to the successful use of APL2 is the need to control the changes of depth which arise from using the operator each with functions such as enclose and disclose. The “spilt pepper” effect following a deluge of “each”'s can be just as damaging as the chains of left-brackets, and of quotes with their accompanying @@@@'s which are the sign of an ISO APL programmer losing his or her mental grip. The temptations of a fast interactive system as a substitute for thought are considerable, and should be resisted. To this end there are places in which informal perceptions of how APL2 functions and operators work can be more valuable than the formal descriptions given in the manuals, and this paper focuses on some points where such pedagogical issues arise. It consists of 4 sections, each with rules or precepts for the disciplined and controlled use of nestedness.

REFERENCES

• 1: J. P. Benkard , J. A. Brown, User defined data types in APL2, Conference proceedings on APL as a tool of thought, p.23-30, July 1989, New York City, New York, United States [doi>10.1145/75144.75149]
• 2: Kenneth E. Iverson, A dictionary of APL, ACM SIGAPL APL Quote Quad, v.18 n.1, p.5-40, September 1, 1987 [doi>10.1145/36983.36984]
• 3: N. D. Thomson, Cultivating trees - an essay in APL2, Proceedings of the international conference on APL, p.343-348, June 11-15, 1984, Finland [doi>10.1145/800058.801119]
• 4: Kenneth E. Iverson , Arthur T. Whitney, Practical uses of a model of APL, Proceedings of the international conference on APL, p.140-145, July 26-30, 1982, Heidelberg, Germany [doi>10.1145/800071.802236]
• 5: J. Philip Benkard, Nonce functions, Conference proceedings on APL 90: for the future, p.27-39, August 13-17, 1990, Copenhagen, Denmark [doi>10.1145/97808.97820]
• 6: N. Thomson, Generic binary trees in APL2, Conference proceedings on APL as a tool of thought, p.364-369, July 1989, New York City, New York, United States [doi>10.1145/75144.75195]

INDEX TERMS

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

          Nouns: APL

Additional Classification:
  D. Software
  D.3 PROGRAMMING LANGUAGES
      D.3.3 Language Constructs and Features
          Subjects: Procedures, functions, and subroutines

General Terms:
Algorithms, Languages