math.c

   1 #include "internal.h"
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4 #include <unistd.h>
   5 #include <math.h>
   6
   7 /* Tiny RPN calculator, because "expr" didn't give me bitwise operations. */
   8
   9 const char                      math_usage[] = "math expression ...";
  10
  11 static double           stack[100];
  12 static unsigned int     pointer;
  13
  14 static void
  15 push(double a)
  16 {
  17         if ( pointer >= (sizeof(stack) / sizeof(*stack)) ) {
  18                 fprintf(stderr, "math: stack overflow\n");
  19                 exit(-1);
  20         }
  21         else
  22                 stack[pointer++] = a;
  23 }
  24
  25 static double
  26 pop()
  27 {
  28         if ( pointer == 0 ) {
  29                 fprintf(stderr, "math: stack underflow\n");
  30                 exit(-1);
  31         }
  32         return stack[--pointer];
  33 }
  34
  35 static void
  36 add()
  37 {
  38         push(pop() + pop());
  39 }
  40
  41 static void
  42 sub()
  43 {
  44         double  subtrahend = pop();
  45
  46         push(pop() - subtrahend);
  47 }
  48
  49 static void
  50 mul()
  51 {
  52         push(pop() * pop());
  53 }
  54
  55 static void
  56 divide()
  57 {
  58         double  divisor = pop();
  59         push(pop() / divisor);
  60 }
  61
  62 static void
  63 and()
  64 {
  65         push((unsigned int)pop() & (unsigned int)pop());
  66 }
  67
  68 static void
  69 or()
  70 {
  71         push((unsigned int)pop() | (unsigned int)pop());
  72 }
  73
  74 static void
  75 eor()
  76 {
  77         push((unsigned int)pop() ^ (unsigned int)pop());
  78 }
  79
  80 static void
  81 not()
  82 {
  83         push(~(unsigned int)pop());
  84 }
  85
  86 static void
  87 print()
  88 {
  89         printf("%g\n", pop());
  90 }
  91
  92 struct op {
  93         const char *    name;
  94         void                    (*function)();
  95 };
  96
  97 static const struct op  operators[] = {
  98         {       "add",  add     },
  99         {       "and",  and     },
 100         {       "div",  divide  },
 101         {       "eor",  eor     },
 102         {       "mul",  mul     },
 103         {       "not",  not     },
 104         {       "or",   or      },
 105         {       "sub",  sub     },
 106         {       0,              0       }
 107 };
 108
 109 static void
 110 stack_machine(const char * argument)
 111 {
 112         char *                          endPointer = 0;
 113         double                          d;
 114         const struct op *       o = operators;
 115
 116         if ( argument == 0 ) {
 117                 print();
 118                 return;
 119         }
 120
 121         d = strtod(argument, &endPointer);
 122
 123         if ( endPointer != argument ) {
 124                 push(d);
 125                 return;
 126         }
 127
 128         while ( o->name != 0 ) {
 129                 if ( strcmp(o->name, argument) == 0 ) {
 130                         (*(o->function))();
 131                         return;
 132                 }
 133                 o++;
 134         }
 135         fprintf(stderr, "math: %s: syntax error.\n", argument);
 136         exit(-1);
 137 }
 138
 139 int
 140 math_main(struct FileInfo * i, int argc, char * * argv)
 141 {
 142         while ( argc >= 2 ) {
 143                 stack_machine(argv[1]);
 144                 argv++;
 145                 argc--;
 146         }
 147         stack_machine(0);
 148         return 0;
 149 }