Function makeDeltaRules

engine/seminaivebottomup.go:365–400

makeDeltaRules creates delta rules to check if newly added facts lead to new derivations.

(decls map[ast.PredicateSym]*ast.Decl, predToRules map[ast.PredicateSym][]ast.Clause)

// makeDeltaRules creates delta rules to check if newly added facts lead to new derivations.
func makeDeltaRules(decls map[ast.PredicateSym]*ast.Decl, predToRules map[ast.PredicateSym][]ast.Clause) map[ast.PredicateSym][]ast.Clause {
	predToDeltaRules := make(map[ast.PredicateSym][]ast.Clause)
	for _, decl := range decls {
		pred := decl.DeclaredAtom.Predicate
		rules := predToRules[pred]
		for _, clause := range rules {
			if clause.Transform != nil && !clause.Transform.IsLetTransform() {
				// Rules with do-transforms are only applied at the very end.
				continue
			}
			var deltaRules []ast.Clause
			for i, subgoal := range clause.Premises {
				// Create delta rule for each subgoal matching positive atoms from last round.
				var pred ast.PredicateSym
				switch p := subgoal.(type) {
				case ast.Atom:
					pred = p.Predicate
				case ast.TemporalLiteral:
					if atom, ok := p.Literal.(ast.Atom); ok {
						pred = atom.Predicate
					}
				}

				if pred.Symbol == "" || pred.IsBuiltin() {
					continue
				}
				if _, ok := decls[pred]; ok {
					deltaRule := makeSingleDeltaRule(clause, i)
					deltaRules = append(deltaRules, deltaRule)
				}
			}
			predToDeltaRules[pred] = append(predToDeltaRules[pred], deltaRules...)
		}
	}
	return predToDeltaRules
}

func (e *engine) hasMergePredicate(pred ast.PredicateSym) (ast.FunDep, ast.PredicateSym, bool) {
	decl := e.predToDecl[pred]