private ConstantValue ApplyUnaryOperation(Expression operand, UnaryOperationKind operationKind)
{
if (operationKind == UnaryOperationKind.LogicalNegation)
{
return(!Evaluate(operand));
}
if (operand.Kind != SyntaxNodeKind.Variable &&
(operationKind == UnaryOperationKind.PostfixIncrement || operationKind == UnaryOperationKind.PostfixIncrement))
{
string op = Operation.GetText(operationKind);
throw new InvalidOperationException($"Unary operator '{op}' can only be applied to variables.");
}
ConstantValue oldValue;
string variableName = string.Empty;
if (operand.Kind == SyntaxNodeKind.Variable)
{
variableName = (operand as Variable).Name.FullName;
oldValue = _env?.GetVariable((operand as Variable).Name.FullName);
}
else
{
oldValue = Evaluate(operand);
}
switch (operationKind)
{
case UnaryOperationKind.UnaryPlus:
return(oldValue);
case UnaryOperationKind.UnaryMinus:
return(-oldValue);
case UnaryOperationKind.PostfixIncrement:
_env.SetVariable(variableName, oldValue++);
return(oldValue);
case UnaryOperationKind.PostfixDecrement:
default:
_env.SetVariable(variableName, oldValue--);
return(oldValue);
}
}
internal override Expression VisitVariable(Variable variable)
{
return(_env.GetVariable(variable.Name.FullName));
}
