denominator.cpp

   1 #include "stdafx.h"
   2 #include "defs.h"
   3
   4 void
   5 eval_denominator(void)
   6 {
   7         push(cadr(p1));
   8         eval();
   9         denominator();
  10 }
  11
  12 void
  13 denominator(void)
  14 {
  15         int h;
  16
  17         save();
  18
  19         p1 = pop();
  20
  21         if (car(p1) == symbol(ADD)) {
  22                 push(p1);
  23                 rationalize();
  24                 p1 = pop();
  25         }
  26
  27         if (car(p1) == symbol(MULTIPLY)) {
  28                 h = tos;
  29                 p1 = cdr(p1);
  30                 while (iscons(p1)) {
  31                         push(car(p1));
  32                         denominator();
  33                         p1 = cdr(p1);
  34                 }
  35                 multiply_all(tos - h);
  36         } else if (isrational(p1)) {
  37                 push(p1);
  38                 mp_denominator();
  39         } else if (car(p1) == symbol(POWER) && isnegativeterm(caddr(p1))) {
  40                 push(p1);
  41                 reciprocate();
  42         } else
  43                 push(one);
  44
  45         restore();
  46 }
  47
  48 #if SELFTEST
  49
  50 static char *s[] = {
  51
  52         "denominator(2/3)",
  53         "3",
  54
  55         "denominator(x)",
  56         "1",
  57
  58         "denominator(1/x)",
  59         "x",
  60
  61         "denominator(a+b)",
  62         "1",
  63
  64         "denominator(1/a+1/b)",
  65         "a*b",
  66
  67         // denominator function expands
  68
  69         "denominator(1/(x-1)/(x-2))",
  70         "x^2-3*x+2",
  71 };
  72
  73 void
  74 test_denominator(void)
  75 {
  76         test(__FILE__, s, sizeof s / sizeof (char *));
  77 }
  78
  79 #endif