Constraint logic programming: Difference between revisions

Revision as of 17:09, 12 November 2009

Revision as of 15:14, 10 February 2010

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===Tree terms===

Constraint logic programming with tree terms emulates regular logic programming by storing substitutions as constraints in the constraint store. Terms are variables, constants, and functorsfunction symbols applied to other terms. The only considered constraints are equalities and disequalities between terms. Equality is particularly important, as constraints link <code>t1=t2</code> are often generated by the interpreter. Equality constraints on terms can be simplified via [[unification]]:

A constraint <code>t1=t2</code> can be simplified if both terms are functors applied to other terms. If the two functors are the same and the number of subterms is also the same, this constraint can be replaced with the pairwise equality of subterms. If the terms are composed of different functors or the same functor but on different number of terms, the constraint is unsatisfiable.