ex_5-10.c

   1 #include <ctype.h>
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4
   5 #define STACKSIZE 100
   6
   7 double stack[STACKSIZE];
   8 int stkh = 0;
   9
  10 void error(const char *err)
  11 {
  12         fprintf(stderr, "ERROR: %s\n", err);
  13         exit(EXIT_FAILURE);
  14 }
  15
  16 void push(double val)
  17 {
  18         if(stkh == STACKSIZE)
  19                 error("Stack Overflow.");
  20         stack[stkh] = val;
  21         ++stkh;
  22 }
  23
  24 double pop()
  25 {
  26         if(stkh == 0)
  27                 error("Stack Empty.");
  28         return stack[--stkh];
  29 }
  30
  31 int main(int argc, char *argv[])
  32 {
  33         int i = 0;
  34         for(i = 1; i < argc; ++i)
  35         {
  36                 switch(argv[i][0])
  37                 {
  38                         case '\0':
  39                                 error("No Arguments Sent.");
  40                                 break;
  41                         case '1':
  42                         case '2':
  43                         case '3':
  44                         case '4':
  45                         case '5':
  46                         case '6':
  47                         case '7':
  48                         case '8':
  49                         case '9':
  50                         case '0':
  51                                 push(atof(argv[i]));
  52                                 break;
  53                         case '+':
  54                                 push(pop()+pop());
  55                                 break;
  56                         case 'x':
  57                                 push(pop()*pop());
  58                                 break;
  59                         default:
  60                                 error("Unknown Operand.");
  61                                 break;
  62                 }
  63         }
  64         printf("%f\n", pop());
  65         return 1;
  66 }