private bool TryHelperFor_MatchkY(Expression x, INumericalAbstractDomainQuery <Variable, Expression> adom,
Expression y, Rational k, out Expression leqExp)
{
Contract.Requires(adom != null);
Contract.Requires(y != null);
Contract.Requires(!object.ReferenceEquals(k, null));
Contract.Ensures(!Contract.Result <bool>() || Contract.ValueAtReturn(out leqExp) != null);
var yPositive = adom.CheckIfGreaterEqualThanZero(y);
if (k >= 1 && yPositive.IsNormal())
{
if (yPositive.BoxedElement)
{
leqExp = expManager.Encoder.CompoundExpressionFor(ExpressionType.Bool, ExpressionOperator.LessEqualThan, y, x);
return(true);
}
else
{
leqExp = expManager.Encoder.CompoundExpressionFor(ExpressionType.Bool, ExpressionOperator.LessEqualThan, x, y);
return(true);
}
}
leqExp = default(Expression);
return(false);
}
public override Set <Expression> VisitOr(Expression left, Expression right, Expression original, INumericalAbstractDomainQuery <Variable, Expression> data)
{
var result = new Set <Expression>();
if (data == null || left == null || right == null)
{
return(result);
}
if (data.CheckIfGreaterEqualThanZero(left).IsTrue() && data.CheckIfGreaterEqualThanZero(right).IsTrue())
{
result.Add(expManager.Encoder.CompoundExpressionFor(ExpressionType.Bool, ExpressionOperator.LessEqualThan, left, x));
result.Add(expManager.Encoder.CompoundExpressionFor(ExpressionType.Bool, ExpressionOperator.LessEqualThan, right, x));
}
return(result);
}
public List <Expression> InferConstraints(Expression x, Expression exp, INumericalAbstractDomainQuery <Variable, Expression> adom)
{
Contract.Ensures(Contract.Result <List <Expression> >() != null);
var result = new List <Expression>();
if (adom == null)
{
return(result);
}
// This may appear straightforward and repeatitive, but sometimes the CheckIfxxx are more precise than what the abstract domain can track
// (because of the refinement of the expressions, and the fact that they are "goal directed")
// As a consequence, we add explicitely this information to the abstract domain
var isGeqZero = adom.CheckIfGreaterEqualThanZero(exp);
if (isGeqZero.IsNormal())
{
var zero = ExpressionManager.Encoder.ConstantFor(0);
if (isGeqZero.IsTrue())
{
// Discovered the disequality : 0 <= x
var newConstraint = ExpressionManager.Encoder.CompoundExpressionFor(ExpressionType.Bool, ExpressionOperator.GreaterEqualThan, x, zero);
result.Add(newConstraint);
}
else
{
// Discovered the disequality : x < 0"
var newConstraint = ExpressionManager.Encoder.CompoundExpressionFor(ExpressionType.Bool, ExpressionOperator.LessThan, x, zero);
result.Add(newConstraint);
}
}
return(result);
}
