decomp.cpp

   1 #include "stdafx.h"
   2 #include "defs.h"
   3
   4 void
   5 eval_decomp(void)
   6 {
   7         int h = tos;
   8         push(symbol(NIL));
   9         push(cadr(p1));
  10         eval();
  11         push(caddr(p1));
  12         eval();
  13         p1 = pop();
  14         if (p1 == symbol(NIL))
  15                 guess();
  16         else
  17                 push(p1);
  18         decomp();
  19         list(tos - h);
  20 }
  21
  22 // returns constant expresions on the stack
  23
  24 void
  25 decomp(void)
  26 {
  27         save();
  28
  29         p2 = pop();
  30         p1 = pop();
  31
  32         // is the entire expression constant?
  33
  34         if (find(p1, p2) == 0) {
  35                 push(p1);
  36                 //push(p1);     // may need later for pushing both +a, -a
  37                 //negate();
  38                 restore();
  39                 return;
  40         }
  41
  42         // sum?
  43
  44         if (isadd(p1)) {
  45                 decomp_sum();
  46                 restore();
  47                 return;
  48         }
  49
  50         // product?
  51
  52         if (car(p1) == symbol(MULTIPLY)) {
  53                 decomp_product();
  54                 restore();
  55                 return;
  56         }
  57
  58         // naive decomp if not sum or product
  59
  60         p3 = cdr(p1);
  61         while (iscons(p3)) {
  62                 push(car(p3));
  63                 push(p2);
  64                 decomp();
  65                 p3 = cdr(p3);
  66         }
  67
  68         restore();
  69 }
  70
  71 void
  72 decomp_sum(void)
  73 {
  74         int h;
  75
  76         // decomp terms involving x
  77
  78         p3 = cdr(p1);
  79
  80         while (iscons(p3)) {
  81                 if (find(car(p3), p2)) {
  82                         push(car(p3));
  83                         push(p2);
  84                         decomp();
  85                 }
  86                 p3 = cdr(p3);
  87         }
  88
  89         // add together all constant terms
  90
  91         h = tos;
  92
  93         p3 = cdr(p1);
  94
  95         while (iscons(p3)) {
  96                 if (find(car(p3), p2) == 0)
  97                         push(car(p3));
  98                 p3 = cdr(p3);
  99         }
 100
 101         if (tos - h) {
 102                 add_all(tos - h);
 103                 p3 = pop();
 104                 push(p3);
 105                 push(p3);
 106                 negate();       // need both +a, -a for some integrals
 107         }
 108 }
 109
 110 void
 111 decomp_product(void)
 112 {
 113         int h;
 114
 115         // decomp factors involving x
 116
 117         p3 = cdr(p1);
 118
 119         while (iscons(p3)) {
 120                 if (find(car(p3), p2)) {
 121                         push(car(p3));
 122                         push(p2);
 123                         decomp();
 124                 }
 125                 p3 = cdr(p3);
 126         }
 127
 128         // multiply together all constant factors
 129
 130         h = tos;
 131
 132         p3 = cdr(p1);
 133
 134         while (iscons(p3)) {
 135                 if (find(car(p3), p2) == 0)
 136                         push(car(p3));
 137                 p3 = cdr(p3);
 138         }
 139
 140         if (tos - h) {
 141                 multiply_all(tos - h);
 142                 //p3 = pop();   // may need later for pushing both +a, -a
 143                 //push(p3);
 144                 //push(p3);
 145                 //negate();
 146         }
 147 }