BinaryRelation

Base class to implement primitives that relate two Terms and provide a single response, sparing implementers from manually pulling first/second out of Solve.Request.arguments and checking the request's arity (always 2, enforced by PrimitiveWrapper).

This class and its nested subclasses form a ladder of increasingly specific (and increasingly convenient) template methods to override, from most to least general:

• BinaryRelation itself -- override computeAll for a fully backtrackable relation producing arbitrarily many Solve.Responses (including side effects), e.g. via Solve.Request.replyWith;

• WithoutSideEffects -- override computeAllSubstitutions for a backtrackable relation with no side effects, producing a Sequence of Substitutions (one per solution);

• NonBacktrackable -- override computeOne for a deterministic relation (no choice points) still able to attach side effects to its single Solve.Response;

• Functional -- override computeOneSubstitution for a deterministic, side-effect-free relation producing a single Substitution;

• Predicative -- override compute for a deterministic, pure test returning true/false (e.g. ==/2).

See the it.unibo.tuprolog.solve.stdlib.primitive implementations (e.g. arithmetic comparisons) for concrete examples of each level.

Inheritors