public static Set <BoxedExpression> ConstantsIfLinearExpression(BoxedExpression exp)
{
Contract.Requires(exp != null);
var visitor = new ConstantsInBoxedExpression();
exp.Dispatch(visitor);
Set <BoxedExpression> result;
if (!visitor.TryGetConstants(out result))
{
result = null;
}
return(result);
}
public bool TryMostGeneralSatisfaction(BoxedExpression input, BoxedExpression var, out BoxedExpression result)
{
BinaryOperator bop;
BoxedExpression left, right;
if (input.IsBinaryExpression(out bop, out left, out right) && bop.IsComparisonBinaryOperator())
{
var leftVars = left.Variables();
var rightVars = right.Variables();
var vIsLeft = (leftVars.Count == 1 && rightVars.Count == 0);
var vIsRight = (leftVars.Count == 0 && rightVars.Count == 1);
if (vIsLeft || vIsRight)
{
// do the swap
if (vIsLeft && bop.TryInvert(out bop))
{
var tmp = right;
right = left;
left = tmp;
}
// Invariant:
// + left has no variables
// + right has exactly one variable
// Build a new expression
var newLeft = left.Sub(ConstantsInBoxedExpression.ConstantsIfLinearExpression(right)).EvaluateConstants(this.MetaDataDecoder);
if (newLeft != null)
{
var newRight = rightVars.PickAnElement();
}
switch (bop)
{
case BinaryOperator.Ceq:
case BinaryOperator.Cge:
case BinaryOperator.Cge_Un:
case BinaryOperator.Cle:
case BinaryOperator.Cle_Un:
{
result = newLeft.EvaluateConstants(this.MetaDataDecoder);
return(true);
}
case BinaryOperator.Cgt:
case BinaryOperator.Cgt_Un:
{
// k > x ==> x == k -1
result = MinusOne(newLeft);
return(true);
}
case BinaryOperator.Clt:
case BinaryOperator.Clt_Un:
{ // k < x ==> x == k+1
result = PlusOne(newLeft);
return(true);
}
}
}
if (leftVars.Count == 1 && rightVars.Count == 1)
{
left = leftVars.PickAnElement();
right = rightVars.PickAnElement();
if (left.Equals(var) && bop.TryInvert(out bop))
{
left = right;
right = var;
}
// invariant the invariant is on the right
if (right.Equals(var))
{
// TODO: merge with the switch above
switch (bop)
{
case BinaryOperator.Ceq:
case BinaryOperator.Cge:
case BinaryOperator.Cge_Un:
case BinaryOperator.Cle:
case BinaryOperator.Cle_Un:
{
result = left;
return(true);
}
case BinaryOperator.Cgt:
case BinaryOperator.Cgt_Un:
{
// k > x ==> x == k -1
result = MinusOne(left);
return(true);
}
case BinaryOperator.Clt:
case BinaryOperator.Clt_Un:
{ // k < x ==> x == k+1
result = PlusOne(right);
return(true);
}
}
}
}
}
result = null;
return(false);
}
