The dual structure of ordered trees

ABSTRACT

Although they were described by K. Iverson in his 1962 book [1], ordered trees have never been implemented as APL objects. However, APL2 as well as ISO-APL, provide many facilities to handle them. This paper illustrates with simple examples, the duality between the tree-structure and what will be presented as an "object-oriented definition structure". APL functions are proposed to facilitate the conversion of one form into the other one. Trees have great utility in data base processing, as well in science, as in business applications. Interfaces with the "outer world" - e.g. word processors, or LISP and PROLOG can become easy to build with the help of this simple concept of duality.

REFERENCES

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• 3: A. Colmerauer, Pro log3 (in press).
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• 8: P. Pujo. "D~veloppement d'une interface convlvlale pour i' interrogation en langage naturel d'une base de donn~es avec utilisatlon des concepts de l'Intelligence artificielle", Th~se de Doctorat, Universlt~ Paris XI, (1989).
• 9: G.A. Langlet. "Presentation of GLOS, all-purpose software integrator on PC", ModelZfng Of Molecular Structures and Properties, Elsevier, ISBN 0-444-88714-8, 767 (1990).
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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.3 PROGRAMMING LANGUAGES
      D.3.3 Language Constructs and Features
          Subjects: Data types and structures

  E. Data
  E.1 DATA STRUCTURES
      Subjects: Trees

General Terms:
Algorithms, Languages, Measurement