Method eval

engine/naivebottomup.go:91–125

This is very inefficient because it generates the same facts over and over again.

()

// This is very inefficient because it generates the same facts over and over again.
func (e naiveEngine) eval() {
	for {
		factadded := false
		for _, clause := range e.programInfo.Rules {
			if clause.Transform != nil {
				continue
			}
			for _, fact := range e.oneStepEvalClause(clause) {
				if e.store.Add(fact) {
					factadded = true
				}
			}
		}
		if !factadded {
			break
		}
	}
	for _, clause := range e.programInfo.Rules {
		if clause.Transform == nil {
			continue
		}
		internalPremise := clause.Premises[0].(ast.Atom)
		var substs []ast.ConstSubstList
		e.store.GetFacts(internalPremise, func(fact ast.Atom) error {
			var subst ast.ConstSubstList
			for i, baseTerm := range internalPremise.Args {
				v, _ := baseTerm.(ast.Variable)
				subst = subst.Extend(v, fact.Args[i].(ast.Constant))
			}
			substs = append(substs, subst)
			return nil
		})
		EvalTransform(clause.Head, *clause.Transform, substs, e.store.Add)
	}
}

// Evaluates clause, by scanning known facts for each premise and producing
// a solution (conjunctive query, similar to a join).