Postfix (reverse polish notation) calculator

hi, I am working on another project. For this one I have to create a reverse polish notation calculator. I have almost everything down but I do not know how to continue. I can only get single integers to read into my program. I do not know how to read in multiple integer numbers or know how to read numbers with decimals in between. the program does not compile either. I need major help. I already spent butt loads of work....

Code:

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <ctype.h>
#include <stdlib.h>
#define  STACKSIZE  6

int  stack_pointer = 0;
int  STACKDISPLAY = 0;
double stack[STACKSIZE] = {0.0};

void
    show_stack(char message[])
{
  /*
   * this printout may be helpful for debugging and understanding what is
   * going on
   */
  int  i;
  if (!STACKDISPLAY)
	{
     return;                 /* return unless STACKDISPLAY is turned on */
	}

  printf("Displaying stack at end of function %s\nStack contents:\n\r", message);
		for (i = stack_pointer; i >= 0; i--)
			printf("stack[%d] = %f\n\r", i, stack[i]);
		printf("\n\n");
}

double
    pop_off_stack(void)
{
  double return_value;
  return_value = stack[stack_pointer]; /* return value on the top of the
                                        * stack */

  if (stack_pointer > 0) /* move the stack pointer down if not at the*/
                           /* lowest point */
		{
			stack_pointer--;
		}

  show_stack("pop_off_stack");

  return return_value;
}

double
    top_of_stack_value(void)
{
  return stack[stack_pointer]; /* just return the value on the top of the
                                * stack */
}

double
    push_onto_stack(double value)
{
  int  i;
  stack[++stack_pointer] = value; /* put value on the top of the stack */


  /*
   * check to see if stack full, if so, move down, causing the bottom value
   * to disappear
   */
  assert(stack_pointer < (STACKSIZE + 1));
  if (stack_pointer == STACKSIZE)
  {
     for (i = 0; i < STACKSIZE; i++)
        stack[i] = stack[i + 1];
     stack_pointer = STACKSIZE - 2; /* maximume of STACKSIZE-2 items max
                                           * on stack */
  }

  show_stack("push_onto_stack");
  return value;
}


int
    main(int argc, char **argv)
{
  char c, instr[80];
  double aDouble;

  while (1)
		{                         /* iterate until input file runs out or user
									* types q or Q */
			c = getchar();
			if (c == EOF)
				{
					break;
				}                         /* end of file was reached, quit processing
											* input */

			if   (isdigit(c))         /* lame way to read a number in  gets one
                                * digit only */
				{
					instr[0] = c;
					instr[1] = '\0';
					aDouble = atof(instr); /* convert string to float */
					push_onto_stack(aDouble);
				}                         /* end of lame way to read a number */

			if ((c == 'q') || (c == 'Q'))
				{
					printf("Quiting.  Bye.\n");
					break;                 /* quit on a Q or q */
				}

			if (c == '+')
				{
					printf("The sum is: %f\n",
					push_onto_stack(pop_off_stack() + pop_off_stack()));
				}
     /*
      * the above statement sums the top two elements on the stack and push the result back onto
      * the stack
      */

			if (c == '-')
				{
					printf("the result is: %f\n", push_onto_stack(pop_off_stack() - pop_off_stack()));
				}
          /*
      * the above statement subtracts the top two elements on the stack and push the result back onto
      * the stack
      */

			if (c == '*')
				{
					printf("the result is: %f\n", push_onto_stack(pop_off_stack() * pop_off_stack()));
				}
     /*
      * the above statement multiplies the top two elements on the stack and push the result back onto
      * the stack
      */

			if (c == '/')
				{
					printf("the result is: %f\n", push_onto_stack(pop_off_stack() / pop_off_stack()));
				}
          /*
      * the above statement multiplies the top two elements on the stack and push the result back onto
      * the stack
      */

			if (c == "chs")
				{
					if (
						{
								push_onto_stack((double)pop_off_stack()*(-1.000000))= -((double)pop_off_stack());
								printf("the result is: %f\n", push_onto_stack((double)pop_off_stack()));
						}
					else if
						{
								push_onto_stack((double)pop_off_stack()*(-1.000000))= ((double)pop_off_stack());
								printf("the result is: %f\n", push_onto_stack((double)pop_off_stack()*(-1.000000)));
						}
				}


			if (c == "abs")
				{
					printf("the result is: %f\n", push_onto_stack(abs((double)pop_off_stack())));
				}

			if (c == "sqrt")
				{
					printf("the result is: %f\n", push_onto_stack(sqrt((double)pop_off_stack())));
				}

			if (c == "sin")
				{
					printf("the result is: %f\n", push_onto_stack(sin((double)pop_off_stack())));
				}

			if (c == "cos")
				{
					printf("the result is: %f\n", push_onto_stack(cos((double)pop_off_stack())));
				}

			if (c == "tan")
				{
					printf("the result is: %f\n", push_onto_stack(tan((double)pop_off_stack())));
				}


}  /* end infinite while */

  return 0;                 /* normal termination */
}

the program does not compile either.

Very informative - show the error messages

Code:

instr[0] = c;
instr[1] = '\0';
aDouble = atof(instr); /* convert string to float */

horrible idea
int res = c - '0';

should do the work better


You better fix the indentation befoer posting

the compiler errors are from if statements that I do not know how to set the conditions of...

Code:

			if (c == "chs")
				{
					if (
						{
								push_onto_stack((double)pop_off_stack()*(-1.000000))= -((double)pop_off_stack());
								printf("the result is: %f\n", push_onto_stack((double)pop_off_stack()));
						}
					else if
						{
								push_onto_stack((double)pop_off_stack()*(-1.000000))= ((double)pop_off_stack());
								printf("the result is: %f\n", push_onto_stack((double)pop_off_stack()*(-1.000000)));
						}
				}

c == "chs"

c is character? you cannot compare it to string

Code:

push_onto_stack((double)pop_off_stack()*(-1.000000))= -((double)pop_off_stack());

what is this? contest howto write most unreadable code?
use temp vars and do it step by step...
then maybe you see your problem, you succed to write the code in a way that really does what you want it to do...

how do you do that?

Originally Posted by ottomated

how do you do that?

do what?

right now I have pointers being compared to characters.
how do I solve that?
how do you use temp vars?

finished it.
its working..

Code:

/*--------------------------------------------------------------------------------------------------------
|       Reverse Polish Calculator
|       Now you can easily calculate numbers
|       Author: Otto Tatsumi, The George Washington University
|       Last modified: May 6th  2008
|       Always Providing You with Simple Elegant Programs Since 2007
--------------------------------------------------------------------------------------------------------*/

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <math.h>
#include <ctype.h>
#include <stdlib.h>
#define  STACKSIZE  6

int  stack_pointer = 0;
int  STACKDISPLAY = 0;
long double stack[STACKSIZE] = {0.0};

int string_equal(const char* first, const char *second)
{
	return (strcmp(first, second) == 0);
}

void
show_stack(char message[])
{
	/*
	 * this printout may be helpful for debugging and understanding what is
	 * going on
	 */
	int  i;
	if (!STACKDISPLAY)
	{
		return;                 /* return unless STACKDISPLAY is turned on */
	}
	
	printf("Displaying stack at end of function %s\nStack contents:\n\r", message);
	for (i = stack_pointer; i >= 0; i--)
		printf("stack[%d] = %f\n\r", i, stack[i]);
	printf("\n\n");
}

double
pop_off_stack(void)
{
	double return_value;
	return_value = stack[stack_pointer]; /* return value on the top of the
		* stack */
	
	if (stack_pointer > 0) /* move the stack pointer down if not at the*/
		/* lowest point */
	{
		stack_pointer--;
	}
	
	show_stack("pop_off_stack");
	
	return return_value;
}

double
top_of_stack_value(void)
{
	return stack[stack_pointer]; /* just return the value on the top of the
	* stack */
}

double
push_onto_stack(double value)
{
	int  i;
	stack[++stack_pointer] = value; /* put value on the top of the stack */
	
	
	/*
	 * check to see if stack full, if so, move down, causing the bottom value
	 * to disappear
	 */
	assert(stack_pointer < (STACKSIZE + 1));
	if (stack_pointer == STACKSIZE)
	{
		for (i = 0; i < STACKSIZE; i++)
			stack[i] = stack[i + 1];
		stack_pointer = STACKSIZE - 2; /* maximume of STACKSIZE-2 items max
			* on stack */
	}
	
	show_stack("push_onto_stack");
	return value;
}


int
main(int argc, char **argv)
{
	char c, instr[80];
	char input[80]; memset(input, '\0', 80);
	double aDouble;
	
	while (1)
	{
		scanf("%s", &input);
		
		long double numericalInput = atof(input);
		
		if(numericalInput == 0.0) 
		{
			// then try parsing the commands, like "chs", "abs", "sin", etc.
			// use the stringEquals() method.
			if(string_equal(input, "+"))
			{
				// addition
				printf(" The sum is %f\n", push_onto_stack(pop_off_stack() + pop_off_stack()));
			} else if (string_equal(input, "-")) {
				// subtraction goes here
				printf(" The sum is %f\n", push_onto_stack(pop_off_stack() - pop_off_stack()));
			} else if (string_equal(input, "*")) {
				//multiplcation here
				printf(" The sum is %f\n", push_onto_stack(pop_off_stack() * pop_off_stack()));
			} else if (string_equal(input, "/")) {
				//division here
				printf( "The sum is %f\n", push_onto_stack(pop_off_stack() / pop_off_stack()));
			} else if (string_equal(input, "chs")) {
				//change signs
				printf( "The number is %f\n", push_onto_stack(pop_off_stack()*(-1)));
			} else if (string_equal(input, "abs")) {
				//absolute value
				printf("the result is: %f\n", push_onto_stack(abs((double)pop_off_stack())));
			} else if (string_equal(input, "sqrt")) {
				//square root here
				printf("the result is: %f\n", push_onto_stack(sqrt((double)pop_off_stack())));
			} else if (string_equal(input, "sin")) {
				//sin function here
				printf("the result is: %f\n", push_onto_stack(sin((double)pop_off_stack())));
			} else if (string_equal(input, "cos")) {
				//cos function here
				printf("the result is: %f\n", push_onto_stack(cos((double)pop_off_stack())));
			} else if (string_equal(input, "tan")) {
				//tan function here
				printf("the result is: %f\n", push_onto_stack(tan((double)pop_off_stack())));
			} else if (string_equal(input, "q") || string_equal(input, "Q")) {
				//quitting program
				printf("Quitting Good Bye \n");
				exit(0);
			}
				
		} else {
			// push the value 'numericalInput' onto the stack.
			push_onto_stack (numericalInput);
		}
	}
	/* end infinite while */

  return 0;                 /* normal termination */
}

//by Otto Tatsumi at the George Washington University