arcsin.cpp

   1 #include "stdafx.h"
   2 #include "defs.h"
   3
   4 void
   5 eval_arcsin(void)
   6 {
   7         push(cadr(p1));
   8         eval();
   9         arcsin();
  10 }
  11
  12 void
  13 arcsin(void)
  14 {
  15         int n;
  16         double d;
  17
  18         save();
  19
  20         p1 = pop();
  21
  22         if (car(p1) == symbol(SIN)) {
  23                 push(cadr(p1));
  24                 restore();
  25                 return;
  26         }
  27
  28         if (isdouble(p1)) {
  29                 errno = 0;
  30                 d = asin(p1->u.d);
  31                 if (errno)
  32                         stop("arcsin function argument is not in the interval [-1,1]");
  33                 push_double(d);
  34                 restore();
  35                 return;
  36         }
  37
  38         // if p1 == 1/sqrt(2) then return 1/4*pi (45 degrees)
  39
  40         if (isoneoversqrttwo(p1)) {
  41                 push_rational(1, 4);
  42                 push_symbol(PI);
  43                 multiply();
  44                 restore();
  45                 return;
  46         }
  47
  48         // if p1 == -1/sqrt(2) then return -1/4*pi (-45 degrees)
  49
  50         if (isminusoneoversqrttwo(p1)) {
  51                 push_rational(-1, 4);
  52                 push_symbol(PI);
  53                 multiply();
  54                 restore();
  55                 return;
  56         }
  57
  58         if (!isrational(p1)) {
  59                 push_symbol(ARCSIN);
  60                 push(p1);
  61                 list(2);
  62                 restore();
  63                 return;
  64         }
  65
  66         push(p1);
  67         push_integer(2);
  68         multiply();
  69         n = pop_integer();
  70
  71         switch (n) {
  72
  73         case -2:
  74                 push_rational(-1, 2);
  75                 push_symbol(PI);
  76                 multiply();
  77                 break;
  78
  79         case -1:
  80                 push_rational(-1, 6);
  81                 push_symbol(PI);
  82                 multiply();
  83                 break;
  84
  85         case 0:
  86                 push(zero);
  87                 break;
  88
  89         case 1:
  90                 push_rational(1, 6);
  91                 push_symbol(PI);
  92                 multiply();
  93                 break;
  94
  95         case 2:
  96                 push_rational(1, 2);
  97                 push_symbol(PI);
  98                 multiply();
  99                 break;
 100
 101         default:
 102                 push_symbol(ARCSIN);
 103                 push(p1);
 104                 list(2);
 105                 break;
 106         }
 107
 108         restore();
 109 }