35.1 Operations on rewriting systems

  • IsRewritingSystem( obj ) C

    This is the category in which all rewriting systems lie.

  • Rules( rws ) A

    The rules comprising the rewriting system. Note that these may change through the life of the rewriting system, however they will always be a set of defining relations of the algebra described by the rewriting system.

  • OrderOfRewritingSystem( rws ) A

    The order of the rewriting system.

  • ReducedForm( rws, u ) O

    Given an element u in the free (or term) algebra over which rws is defined, rewrite u by successive applications of the rules of rws until no further rewriting is possible, and return the resulting element of T.

  • IsConfluent( rws ) P
  • IsConfluent( A ) P

    Checks whether the rewriting system rws is confluent. A rewriting system is confluent if, for every two words u and v in the free algebra T which represent the same element of the algebra A defined by rws, ReducedForm(rws,u) = ReducedForm(rws,v) as words in the free algebra T. This element is the unique normal form of the element represented by u.

    In its second form, if A is an algebra with a canonical rewriting system associated with it, it checks whether that rewriting system is confluent.

  • ConfluentRws( rws ) A

    Return a new rewriting system defining the same algebra as rws which is confluent.

  • IsReduced( rws ) P

    A rewriting system is reduced if for each rule (l, r), l and r are both reduced.

  • ReduceRules( rws ) O

    Reduce rules and remove redundant rules to make rws reduced.

  • AddRule( rws, rule ) O

    Add rule to a rewriting system rws.

  • AddRuleReduced( rws, rule ) O

    Add rule to rewriting system rws. Performs a reduction operation on the resulting system, so that if rws is reduced it will remain reduced.

  • MakeConfluent( rws ) O

    Add rules (and perhaps reduce) in order to make rws confluent

  • GeneratorsOfRws( rws ) A

  • AddGenerators( rws, gens ) O

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    GAP 4 manual
    February 2000