On Safe Folding

Annalisa Bossi, Nicoletta Cocco, Sandro Etalle

    Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

    13 Citations (Scopus)
    96 Downloads (Pure)


    In [3] a general fold operation has been introduced for definite programs wrt computed answer substitution semantics. It differs from the fold operation defined by Tamaki and Sato in [26,25] because its application does not depend on the transformation history. This paper extends the results in [3] by giving a more powerful sufficient condition for the preservation of computed answer substitutions. Such a condition is meant to deal with the critical case when the atom introduced by folding depends on the clause to which the fold applies. The condition compares the dependency degree between the fonding atom and the folded clause, with the semantic delay between the folding atom and the ones to be folded. The result is also extended to a more general replacement operation, by showing that it can be decomposed into a sequence of definition, general folding and unfolding operations.
    Original languageEnglish
    Title of host publicationProgramming Language Implementation and Logic Programming
    Subtitle of host publication4th International Symposium, PLILP'92 Leuven, Belgium, August 26–28, 1992 Proceedings
    EditorsMaurice Bruynooghe, Martin Wirsing
    Place of PublicationBerlin, Heidelberg
    Number of pages15
    ISBN (Electronic)978-3-540-47297-1
    ISBN (Print)978-3-540-55844-6
    Publication statusPublished - 1992
    Event4th International Symposium on Programming Language Implementation and Logic Programming, PLILP 1992 - Leuven, Belgium
    Duration: 26 Aug 199228 Aug 1992
    Conference number: 4

    Publication series

    NameLecture Notes in Computer Science
    ISSN (Print)0302-9743
    ISSN (Electronic)1611-3349


    Conference4th International Symposium on Programming Language Implementation and Logic Programming, PLILP 1992
    Abbreviated titlePLILP


    • Program transformation
    • Folding
    • Computed answer substitution semantics


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