public string VisitBinaryExpr(BinaryExpr expr)
{
return(Parenthesize(expr.Operator.Lexeme, expr.Left, expr.Right));
}
public void VisitBinaryExpr(BinaryExpr expr)
{
Resolve(expr.Left);
Resolve(expr.Right);
}
public object VisitBinaryExpr(BinaryExpr expr)
{
var left = Evaluate(expr.Left);
var right = Evaluate(expr.Right);
switch (expr.Operator.Type)
{
case TokenType.Greater:
CheckNumberOperands(expr.Operator, left, right);
return((double)left > (double)right);
case TokenType.GreaterEqual:
CheckNumberOperands(expr.Operator, left, right);
return((double)left >= (double)right);
case TokenType.Less:
CheckNumberOperands(expr.Operator, left, right);
return((double)left < (double)right);
case TokenType.LessEqual:
CheckNumberOperands(expr.Operator, left, right);
return((double)left <= (double)right);
case TokenType.BangEqual:
return(!IsEqual(left, right));
case TokenType.EqualEqual:
return(IsEqual(left, right));
case TokenType.Minus:
CheckNumberOperands(expr.Operator, left, right);
return((double)left - (double)right);
case TokenType.Plus:
if (left is double && right is double)
{
return((double)left + (double)right);
}
if (left is string && right is string)
{
return((string)left + (string)right);
}
if (left is string)
{
return((string)left + Stringify(right));
}
if (right is string)
{
return(Stringify(left) + (string)right);
}
throw new RuntimeError(expr.Operator, "Operands must be two numbers or at least one string.");
case TokenType.Slash:
CheckNumberOperands(expr.Operator, left, right);
return((double)left / (double)right);
case TokenType.Star:
CheckNumberOperands(expr.Operator, left, right);
return((double)left * (double)right);
}
// unreachable
return(null);
}
