calc_adv.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <ctype.h>
   4
   5 #define MAXOP 100
   6 #define NUMBER '0'
   7 #define MAXVAL 100
   8 #define BUFSIZE 100
   9
  10 int getop(char[]);
  11 void push(double);
  12 double pop(void);
  13 void print_stack(void);
  14 void reverse(void);
  15 int getch(void);
  16 void ungetch(int);
  17
  18
  19 char buf[BUFSIZE];
  20 int bufp = 0;
  21 int sp = 0;
  22 double val[MAXVAL];
  23
  24 int main()
  25 {
  26         int type;
  27         double op2;
  28         char s[MAXOP];
  29
  30         while((type = getop(s)) != EOF)
  31         {
  32                 switch(type)
  33                 {
  34                         case NUMBER:
  35                                 push(atof(s));
  36                                 break;
  37                         case 'S':
  38                         case 's':
  39                                 printf("Print Top of Stack\n");
  40                                 print_stack();
  41                                 break;
  42                         case 'R':
  43                         case 'r':
  44                                 printf("Reverse Stack\n");
  45                                 reverse();
  46                                 break;
  47                         case '+':
  48                                 push(pop() + pop());
  49                                 break;
  50                         case '*':
  51                                 push(pop() * pop());
  52                                 break;
  53                         case '-':
  54                                 op2 = pop();
  55                                 push(pop() - op2);
  56                                 break;
  57                         case '/':
  58                                 op2 = pop();
  59                                 if(op2 != 0.0)
  60                                         push(pop() / op2);
  61                                 else
  62                                         printf("error: zero divisor\n");
  63                                 break;
  64                         case '%':
  65                                 op2 = pop();
  66                                 if(op2 != 0.0)
  67                                 {
  68                                         push((int)(pop()) % (int)(op2));
  69                                 } else {
  70                                         printf("error: zero divisor\n");
  71                                 }
  72                                 break;
  73                         case '\n':
  74                                 printf("\t%.8g\n", pop());
  75                                 break;
  76                         default:
  77                                 printf("error: unknown command %s\n", s);
  78                                 break;
  79                 }
  80         }
  81         return 0;
  82 }
  83
  84 /* push f onto value stack */
  85 void push(double f)
  86 {
  87         if(sp < MAXVAL)
  88                 val[sp++] = f;
  89         else
  90                 printf("error: stack full\n");
  91 }
  92
  93 /* pop and return top value from stack */
  94 double pop(void)
  95 {
  96         if(sp > 0)
  97                 return val[--sp];
  98         else
  99         {
 100                 printf("error: stack empty\n");
 101                 return 0.0;
 102         }
 103 }
 104
 105 /* reverse two vales at top of stack */
 106 void reverse()
 107 {
 108         double temp1, temp2;
 109         temp1 = pop();
 110         temp2 = pop();
 111         push(temp1);
 112         push(temp2);
 113 }
 114
 115 /* print top two values on stack */
 116 void print_stack()
 117 {
 118         printf("%f\t%f\n", val[sp], val[sp-1]);
 119 }
 120
 121 /* get next operator or numberic operand */
 122 int getop(char s[])
 123 {
 124         int i, c;
 125
 126         while ((s[0] = c = getch()) == ' ' || c == '\t')
 127                 ;
 128         s[1] = '\0';
 129         if(!isdigit(c) && c != '.')
 130                 return c;
 131         i = 0;
 132         if(isdigit(c))
 133                 while(isdigit(s[++i] = c = getch()))
 134                         ;
 135         if(c == '.')
 136                 while(isdigit(s[++i] = c = getch()))
 137                         ;
 138         s[i] = '\0';
 139         if(c != EOF)
 140                 ungetch(c);
 141         return NUMBER;
 142 }
 143
 144 int getch(void)
 145 {
 146         return (bufp > 0) ? buf[--bufp] : getchar();
 147 }
 148
 149 void ungetch(int c)
 150 {
 151         if(bufp >= BUFSIZE)
 152                 printf("ungetch: too many characters\n");
 153         else
 154                 buf[bufp++] = c;
 155 }