RPN Calculator in C. A little modification needed.

[Peon666]

Homework Statement

To implement an RPN (Reverse Polish Notation) calculator in C language.

Homework Equations

Implement with the help of Stacks and Pinters. No linked lists or Queues. Keep it simple.

The Attempt at a Solution

Here's my code: (only the driver programe)

int main(int argc, char *argv[])
{
int i, rc;
char elements[5];
char *ptr;
int array[2];
int array2[2];
int temp, temp2;

stack_elem_t elem;
stackADT mystack = NULL;

printf ("Enter five elements, operants and operators included.\n");
for (i=0; i<5; i++)
{
scanf ("%s", &elements);
if (isdigit(elements))
{
// array = strtol (elements, &ptr , 0);
array = elements - '0';
push(mystack, array);
}
if (!isdigit(elements))
{
switch (elements)
{
case '+':
if (i < 2)
printf ("Not enough operators to perform addition operation!\n");
array2[0] = pop(mystack, &array[0]); // Output: 1
array2[1] = pop(mystack, &array[1]); // Output: 1
printf ("%d\n", array[0]); // Output: 3 (as I entered)
printf ("%d\n", array[1]); // Output: 4 (as I entered)
temp = (array[0]+array[1]);
push (mystack, temp);
printf ("%d\n", temp); // Output: 1
temp2 = pop (mystack, &temp);
printf ("%d\n",temp2); // Output: 1
break;

And MAIN problem is:

Now the problem is that this does not add the two integers. Why is this happening? Besides, it does not take anything in array2[0] and array2[1]. When I pop the elements array[0] and array[1] into array2[0] and array2[1] and print them out, only 1 is printed out. What could be the problem?

Further, when I add array[0] and array[1] into temp and print temp out, again, 1 is printed and nothing else. However, if I print out array[0] and array[1] separately, they are displayed as I enter them, i.e 3 and 4.

What's going on? I'm really troubled about this fiasco! HELP ME OUT! :(

 

[nvn]

Duplicate of thread [thread=334486]334486[/thread].

 

[Mene]

It seems like there may be a few issues with your code. First, it looks like you are not initializing your stack properly. In your main function, you have declared a stackADT variable called "mystack" but you have not actually allocated any memory for it. This means that when you try to push elements onto the stack, it is essentially pushing them onto nothing. To fix this, you can use the "create_stack" function to create a new stack and assign it to your "mystack" variable.

Another issue may be with your use of the "pop" function. In your code, you are passing in the address of the "array" variable as the second parameter for the "pop" function. This means that the "pop" function will try to assign the value of the popped element to the address of "array". However, "array" is an integer array, so it does not have a specific address that can be assigned to. To fix this, you can declare a temporary variable and pass its address as the second parameter for the "pop" function.

Additionally, it looks like you may not be using the "array2" variable at all. You are popping two elements from the stack and assigning them to "array[0]" and "array[1]", but then you are not using those values in your addition operation. Instead, you are using the values from "array2[0]" and "array2[1]", which have not been assigned any values. To fix this, you can either use the values from "array[0]" and "array[1]" or assign the values from "array[0]" and "array[1]" to "array2[0]" and "array2[1]" respectively before performing the addition operation.

Finally, it may be helpful to print out the contents of your stack at various points in your code to see if the elements are being pushed and popped correctly. This can help you identify any other issues with your code.

I hope this helps you in modifying your code and implementing the RPN calculator successfully. Good luck!