protected override Expression VisitBinary(Binary B)
{
// Logic operators are mostly constant.
if (B.IsLogicOp)
return 0;
return base.VisitBinary(B);
}
protected override PrettyString VisitBinary(Binary B)
{
return(PrettyString.ConcatColumns(Visit(B.Left), Binary.ToString(B.Operator), Visit(B.Right)));
}
protected override Expression VisitBinary(Binary B)
{
Expression L = Visit(B.Left);
Expression R = Visit(B.Right);
// Evaluate substitution operators.
if (B is Substitute)
return Visit(L.Substitute(Set.MembersOf(R).Cast<Arrow>()));
Real? LR = AsReal(L);
Real? RR = AsReal(R);
// Evaluate relational operators on constants.
if (LR != null && RR != null)
{
switch (B.Operator)
{
case Operator.Equal: return Constant.New(LR.Value == RR.Value);
case Operator.NotEqual: return Constant.New(LR.Value != RR.Value);
case Operator.Less: return Constant.New(LR.Value < RR.Value);
case Operator.Greater: return Constant.New(LR.Value <= RR.Value);
case Operator.LessEqual: return Constant.New(LR.Value > RR.Value);
case Operator.GreaterEqual: return Constant.New(LR.Value >= RR.Value);
case Operator.ApproxEqual: return Constant.New(
LR.Value == RR.Value ||
Real.Abs(LR.Value - RR.Value) < 1e-12 * Real.Max(Real.Abs(LR.Value), Real.Abs(RR.Value)));
}
}
// Evaluate boolean operators if possible.
switch (B.Operator)
{
case Operator.And:
if (IsFalse(LR) || IsFalse(RR))
return Constant.New(false);
else if (IsTrue(LR) && IsTrue(RR))
return Constant.New(true);
break;
case Operator.Or:
if (IsTrue(LR) || IsTrue(RR))
return Constant.New(true);
else if (IsFalse(LR) && IsFalse(RR))
return Constant.New(false);
break;
case Operator.Equal:
case Operator.ApproxEqual:
if (L.Equals(R))
return Constant.New(true);
break;
case Operator.NotEqual:
if (L.Equals(R))
return Constant.New(false);
break;
}
return Binary.New(B.Operator, L, R);
}
/// <summary>
/// Create a new inverse unary expression. Inverse(x) -> 1/x.
/// </summary>
/// <param name="Operand"></param>
/// <returns></returns>
public static Expression Inverse(Expression Operand)
{
return(Binary.Power(Operand, -1));
}
protected override string VisitBinary(Binary B)
{
int pr = Parser.Precedence(B.Operator);
return(Visit(B.Left, pr) + ToString(B.Operator) + Visit(B.Right, pr));
}
protected override string VisitBinary(Binary B)
{
int pr = Parser.Precedence(B.Operator);
return Visit(B.Left, pr) + ToString(B.Operator) + Visit(B.Right, pr);
}
public static LazyExpression operator >=(LazyExpression L, LazyExpression R)
{
return(new LazyExpression(Binary.GreaterEqual(L.value, R.value)));
}
public static LazyExpression operator <(LazyExpression L, LazyExpression R)
{
return(new LazyExpression(Binary.Less(L.value, R.value)));
}