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Transforming Boolean equalities into constraints

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Formal Aspects of Computing

Abstract

Although functional as well as logic languages use equality to discriminate between logically different cases, the operational meaning of equality is different in such languages. Functional languages reduce equational expressions to their Boolean values, True or False, logic languages use unification to check the validity only and fail otherwise. Consequently, the language Curry, which amalgamates functional and logic programming features, offers two kinds of equational expressions so that the programmer has to distinguish between these uses. We show that this distinction can be avoided by providing an analysis and transformation method that automatically selects the appropriate operation. Without this distinction in source programs, the language design can be simplified and the execution of programs can be optimized. As a consequence, we show that one kind of equational expressions is sufficient and unification is nothing else than an optimization of Boolean equality.

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Authors and Affiliations

  1. Computer Science Dept., Portland State University, Oregon, USA

    Sergio Antoy

  2. Institut für Informatik, CAU Kiel, 24098, Kiel, Germany

    Michael Hanus

Authors
  1. Sergio Antoy
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  2. Michael Hanus
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Correspondence to Michael Hanus.

Additional information

Augusto Sampaio and Moreno Falashi

This material is based in part upon work supported by the National Science Foundation under Grant No. 1317249.

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Antoy, S., Hanus, M. Transforming Boolean equalities into constraints. Form Asp Comp 29, 475–494 (2017). https://doi.org/10.1007/s00165-016-0399-6

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