Thread: Overflow in Stack Counter

Or! if you REALLY wanted to be creative (which I am all about)

Example:

Code:

typedef float (*operation)(float, float);

float add(float a, float b) { return a + b; }
float sub(float a, float b) { return a - b; }
float mul(float a, float b) { return a * b; }
float div(float a, float b) { return a / b; }

operation isoperator(int c)
{
  switch(c)
  {
    case '+': return add;
    case '-': return sub;
    case '*': return mul;
    case '/': return div;
    default: return 0;
  }
}

/* Then in your for loop */
for(i = 0; i < strlen(input); ++i)
{
  operation op = isoperator(input[i]);

  if(op)
    push((&stk), (*op)(pop(&stk),pop(&stk)));
  else if(isdigit(input[i]))
    push(&stk, (input[i] - '0'));
}

Viola.

Well he opted not to use it at all. I was just trying to copy and paste and spew forth my two cents. Where is the love?

Originally Posted by Elysia

I might probably have written it along the lines of this:

Code:

typedef float (operation_ptr)(float, float);

float add(float a, float b) { return a + b; }
float sub(float a, float b) { return a - b; }
float mul(float a, float b) { return a * b; }
float div(float a, float b) { return a / b; }

operation_ptr* get_op_function(int c)
{
    switch(c)
    {
        case '+': return &add;
        case '-': return ⊂
        case '*': return &mul;
        case '/': return ÷
        default: return NULL;
    }
}

/* Then in your for loop */
for(i = 0; i < strlen(input); i++)
{
    operation_ptr* pOp = get_op_function(input[i]);

    if (pOp)
        push(&stk, pOp( pop(&stk),pop(&stk) ));
    else if ( isdigit(input[i]) )
        push( &stk, (input[i] - '0') );
}

Especially, the name is_operator is misleading (since it returns a function pointer) and the syntax for invoking the function pointer is a little more verbose than necessary.
But I fear we are at a level that is beyond the understanding of the OP...

I'm learning...

The compilation is throwing me a syntax error within the calculate function:

Code:

float calculate(char *postfix)
{
   char *operation;
   stack_type stk;
   int operand1;
   int operand2;
   float sum;
   stk.top = -1;
   operation = &postfix[0];

   while(1)
   {
      if (strcmp(operation, "exit\n") == 0)
      {
         printf("Time to quit...goodbye!\n");
         exit(0);
      }

      else if {                          <-------------------------------- "expected '(' before '{' token"
           switch(*operation)
           {
           case '0':
           case '1':
           case '2':
           case '3':
           case '4':
           case '5':
           case '6':
           case '7':
           case '8':
           case '9':
              push(&stk, (*operation - 48));
                      break;
           }
           }
      else if
      {                                                <-------------------------------- "expected '(' before '{' token"
         operand1 = pop(&stk);
         operand2 = pop(&stk);


            switch(*operation)
            {
            case '+':
               sum = operand1 + operand2;
            break;
            case '-':
               sum = operand1 - operand2;
            break;
            case '/':
               sum = operand1 / operand2;
            break;
            case '*':
               sum = operand1 * operand2;
            break;
            case '%':
               sum = operand1 % operand2;
            break;
            default:
               printf("Epic Fail...invalid input.\n");
            return 0;
            }
         push(&stk, sum);

      operation++;
   }
   sum = pop(&stk);
   }
   return sum;
}

I checked my parenthetic matching and I do not appear to be missing one. Am I syntactically incorrectly declaring a variable?

Originally Posted by mlsrar

I'm learning...

The compilation is throwing me a syntax error within the calculate function:


I checked my parenthetic matching and I do not appear to be missing one. Am I syntactically incorrectly declaring a variable?

Of course you're missing one, you just happen to be missing the ) as well later on. Once you say "if" you need to say if "what". If you just mean else, then just say else, not else if.

Heh... logic errors are fun.

Should I go to the store
Or go to
Or go to
Or

Or go where? Same type of thing dude. And thank you for the corrections Elysia, I actually do appreciate it since 99.95% of the time I just write code in a response and never compile it or anything. "You're a genius programming master! THANKS THANKS THANKS" (I figured I may as well combine all your fan fare)