/*
* The method Skolemize performs best-effort skolemization of the input expression expr.
* If polarity == Polarity.Negative, a quantifier F embedded in expr is skolemized
* provided it can be proved that F is a forall quantifier in the NNF version of expr.
* If polarity == Polarity.Positive, a quantifier F embedded in expr is skolemized
* provided it can be proved that F is an exists quantifier in the NNF version of expr.
*
* Factorization is performed on the resulting expression.
*/
public static VCExpr Skolemize(QuantifierInstantiationEngine qiEngine, Polarity polarity, VCExpr vcExpr)
{
var skolemizer = new Skolemizer(qiEngine, polarity, vcExpr);
var skolemizedExpr = skolemizer.Mutate(vcExpr, true);
return(Factorizer.Factorize(qiEngine, QuantifierCollector.Flip(polarity), skolemizedExpr));
}
public static HashSet <VCExprQuantifier> CollectQuantifiers(VCExpr vcExpr, Polarity polarity)
{
var visitor = new QuantifierCollector();
visitor.Traverse(vcExpr, polarity);
return(visitor.quantifiers);
}
private Factorizer(QuantifierInstantiationEngine qiEngine, Polarity polarity, VCExpr vcExpr) : base(qiEngine.vcExprGen)
{
this.qiEngine = qiEngine;
this.quantifiers = QuantifierCollector.CollectQuantifiers(vcExpr, polarity);
}
private Skolemizer(QuantifierInstantiationEngine qiEngine, Polarity polarity, VCExpr vcExpr) : base(qiEngine.vcExprGen)
{
this.qiEngine = qiEngine;
this.quantifiers = QuantifierCollector.CollectQuantifiers(vcExpr, polarity);
this.bound = new Dictionary <VCExprVar, VCExpr>();
}