private Expr Postfix()
{
Expr expression = Primary();
while (Match(TokenType.MinusMinus, TokenType.PlusPlus))
{
expression = new Expr.Postfix(Previous(), expression);
}
return(expression);
}
public object Visit(Expr.Postfix postfix)
{
object right = Evaluate(postfix.lhs);
ValidateNumberOperand(postfix.opp, right);
switch (postfix.opp.type)
{
case TokenType.MinusMinus:
right = (double)right - 1;
break;
case TokenType.PlusPlus:
right = (double)right + 1;
break;
}
/// This was made up by me because in the book there is nothing that assigns this value.
// Cast to variable type
Expr.Variable asVariable = (Expr.Variable)postfix.lhs;
// Assign it's value
m_Enviroment.Assign(asVariable.name, right);
// Return the value.
return(right);
}
public object Visit(Expr.Postfix _postfix)
{
return(null);
}
string Expr.IVisitor <string> .Visit(Expr.Postfix postfix)
{
return(Parenthesize(postfix.opp.lexeme, postfix.lhs));
}
