public object visitBinaryExpr(Expr.Binary expr)
{
object left = Evaluate(expr.left);
object right = Evaluate(expr.right);
if (expr.op.type == TokenType.AND)
{
return(GetTruthValue(left) && GetTruthValue(right));
}
if (expr.op.type == TokenType.OR)
{
return(GetTruthValue(left) || GetTruthValue(right));
}
// same for strings, numbers and bools
switch (expr.op.type)
{
case TokenType.EQUAL_EQUAL:
return(IsEqual(left, right));
case TokenType.BANG_EQUAL:
return(!IsEqual(left, right));
}
// string specific
if (left is string || right is string)
{
if (expr.op.type != TokenType.PLUS)
{
throw new RuntimeError(expr.op, expr.op.type.ToString() + " not a valid operator on strings.");
}
return(Stringify(left) + Stringify(right));
}
// number specific
CheckNumberOperands(expr.op, left, right);
switch (expr.op.type)
{
case TokenType.PLUS:
return((double)left + (double)right);
case TokenType.MINUS:
return((double)left - (double)right);
case TokenType.STAR:
return((double)left * (double)right);
case TokenType.SLASH:
double r = (double)right;
if (r == 0)
{
throw new RuntimeError(expr.op, "Divide by zero error.");
}
return((double)left / r);
case TokenType.GREATER:
return((double)left > (double)right);
case TokenType.GREATER_EQUAL:
return((double)left >= (double)right);
case TokenType.LESS:
return((double)left < (double)right);
case TokenType.LESS_EQUAL:
return((double)left <= (double)right);
default:
Lox.ReportError(expr.op, expr.op.type.ToString() + " not a valid operator on doubles.");
return(right);
}
}