/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact [email protected]
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdlib.h>
#include<stdio.h>
#include<ctype.h>
#include<math.h>
#include <string.h>

#define MAXOP 100
#define NUMBER       0
#define IDENTIFIER   1
#define TRUE 1
#define FALSE 0



int Getop(char s[]);
void push(double val);
double pop(void);
void showTop(void);
void duplicate(void);
void swapItems(void);
void clearStack();
void mathfnc(char s[]);

int main(void)
{
 int type;
 double op2;
 char s[MAXOP];
 int flag = TRUE;

 while((type = Getop(s)) != EOF)
 {
  switch(type)
  {
  case NUMBER:
   push(atof(s));
   break;
  case IDENTIFIER:
   mathfnc(s);
   break;
  case '+':
  push(pop() + pop());
  break;
  case '*':
   push(pop() * pop());
   break;
  case '-':
   op2 = pop();
   push(pop()- op2);
   break;
  case '/':
   op2 = pop();
   if(op2)
    push(pop() / op2);
   else
    printf("nError: division by zero!");
   break;
  case '%':
   op2 = pop();
   if(op2)
    push(fmod(pop(), op2));
   else
    printf("nError: division by zero!");
   break;
  case '?':
   showTop();
   break;
  case '#':
   duplicate();
   break;
  case '~':
   swapItems();
   break;
  case '!':
   clearStack();
  case 'n':
   printf("nt%.8gn", pop());
   break;
  default:
   printf("nError: unknown command %s.n", s);
   break;
  }
 }
 return EXIT_SUCCESS;
}

#define MAXVAL 100

int sp = 0;         
double val[MAXVAL]; 

/* push: push f onto stack. */
void push(double f)
{
 if(sp < MAXVAL)
  val[sp++] = f;
 else
  printf("nError: stack full can't push %gn", f);
}

/*pop: pop and return top value from stack.*/
double pop(void)
{
 if(sp > 0)
  return val[--sp];
 else
 {
  printf("nError: stack emptyn");
  return 0.0;
 }
}

void showTop(void)
{
 if(sp > 0)
  printf("Top of stack contains: %8gn", val[sp-1]);
 else
  printf("The stack is empty!n");
}



void duplicate(void)
{
 double temp = pop();

 push(temp);
 push(temp);
}

void swapItems(void)
{
 double item1 = pop();
 double item2 = pop();

 push(item1);
 push(item2);
}

void clearStack(void)
{
 sp = 0;
}

/*check string s for supported math functions */
void mathfnc(char s[])
{
 double op2;

 if( 0 == strcmp(s, "sin"))
  push(sin(pop()));
 else if( 0 == strcmp(s, "cos"))
  push(cos(pop()));
 else if (0 == strcmp(s, "exp"))
  push(exp(pop()));
 else if(!strcmp(s, "pow"))
 {
  op2 = pop();
  push(pow(pop(), op2));
 }
 else
  printf("%s Error: is not a supported function.n", s);
}

int getch(void);
void unGetch(int);

/* Getop: get next operator or numeric operand. */
int Getop(char s[])
{
 int i = 0;
 int c;
 int next;


 /* Skip whitespace */
 while((s[0] = c = getch()) == ' ' || c == 't')
  ;
 s[1] = '';

 if(isalpha(c))
 {
  i = 0;
  while(isalpha(s[i++] = c ))
   c = getch();     
  s[i - 1] = '';
  if(c != EOF)
   unGetch(c);
  return IDENTIFIER;
 }

 /* Not a number but may contain a unary minus. */
 if(!isdigit(c) && c != '.' && c != '-')
  return c;                 

 if(c == '-')
 {
  next = getch();
  if(!isdigit(next) && next != '.')
  {
   return c;
  }
  c = next;
 }
 else
  c = getch();

 while(isdigit(s[++i] = c))
  c = getch();
 if(c == '.')                 /* Collect fraction part. */
  while(isdigit(s[++i] = c = getch()))
   ;
 s[i] = '';
 if(c != EOF)
  unGetch(c);
 return NUMBER;
}

#define BUFSIZE 100

char buf[BUFSIZE];
int bufp = 0;
int getch(void)
{
 return (bufp > 0) ? buf[--bufp]: getchar();
}


void unGetch(int c)
{
 if(bufp >= BUFSIZE)
  printf("nUnGetch: too many charactersn");
 else
  buf[bufp++] = c;
}

Read more Similar C Programs
C Basic
C Strings
K and R C Programs Exercise

You can easily select the code by double clicking on the code area above.

To get regular updates on new C programs, you can Follow @c_program

You can discuss these programs on our Facebook Page. Start a discussion right now,

our page!

Share this program with your Facebook friends now! by liking it

(you can send this program to your friend using this button)

Like to get updates right inside your feed reader? Grab our feed!