runtime/ieee_754.js

   1 // Js_of_ocaml runtime support
   2 // http://www.ocsigen.org/js_of_ocaml/
   3 // Copyright (C) 2010 Jérôme Vouillon
   4 // Laboratoire PPS - CNRS Université Paris Diderot
   5 //
   6 // This program is free software; you can redistribute it and/or modify
   7 // it under the terms of the GNU Lesser General Public License as published by
   8 // the Free Software Foundation, with linking exception;
   9 // either version 2.1 of the License, or (at your option) any later version.
  10 //
  11 // This program is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU Lesser General Public License for more details.
  15 //
  16 // You should have received a copy of the GNU Lesser General Public License
  17 // along with this program; if not, write to the Free Software
  18 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19
  20 //Provides: caml_int64_bits_of_float const
  21 function caml_int64_bits_of_float (x) {
  22   if (!isFinite(x)) {
  23     if (isNaN(x)) return [255, 1, 0, 0xfff0];
  24     return (x > 0)?[255,0,0,0x7ff0]:[255,0,0,0xfff0];
  25   }
  26   var sign = (x>=0)?0:0x8000;
  27   if (sign) x = -x;
  28   var exp = Math.floor(Math.LOG2E*Math.log(x)) + 1023;
  29   if (exp <= 0) {
  30     exp = 0;
  31     x /= Math.pow(2,-1026);
  32   } else {
  33     x /= Math.pow(2,exp-1027);
  34     if (x < 16) { x *= 2; exp -=1; }
  35     if (exp == 0) { x /= 2; }
  36   }
  37   var k = Math.pow(2,24);
  38   var r3 = x|0;
  39   x = (x - r3) * k;
  40   var r2 = x|0;
  41   x = (x - r2) * k;
  42   var r1 = x|0;
  43   r3 = (r3 &0xf) | sign | exp << 4;
  44   return [255, r1, r2, r3];
  45 }
  46 //Provides: caml_int64_float_of_bits const
  47 function caml_int64_float_of_bits (x) {
  48   var exp = (x[3] & 0x7fff) >> 4;
  49   if (exp == 2047) {
  50       if ((x[1]|x[2]|(x[3]&0xf)) == 0)
  51         return (x[3] & 0x8000)?(-Infinity):Infinity;
  52       else
  53         return NaN;
  54   }
  55   var k = Math.pow(2,-24);
  56   var res = (x[1]*k+x[2])*k+(x[3]&0xf);
  57   if (exp > 0) {
  58     res += 16
  59     res *= Math.pow(2,exp-1027);
  60   } else
  61     res *= Math.pow(2,-1026);
  62   if (x[3] & 0x8000) res = - res;
  63   return res;
  64 }
  65 //Provides: caml_classify_float const
  66 function caml_classify_float (x) {
  67   if (isFinite (x)) {
  68     if (Math.abs(x) >= 2.2250738585072014e-308) return 0;
  69     if (x != 0) return 1;
  70     return 2;
  71   }
  72   return isNaN(x)?4:3;
  73 }
  74 //Provides: caml_modf_float const
  75 function caml_modf_float (x) {
  76   if (isFinite (x)) {
  77     var neg = (1/x) < 0;
  78     x = Math.abs(x);
  79     var i = Math.floor (x);
  80     var f = x - i;
  81     if (neg) { i = -i; f = -f; }
  82     return [0, f, i];
  83   }
  84   if (isNaN (x)) return [0, NaN, NaN];
  85   return [0, 1/x, x];
  86 }
  87 //Provides: caml_ldexp_float const
  88 function caml_ldexp_float (x,exp) {
  89   exp |= 0;
  90   if (exp > 1023) {
  91     exp -= 1023;
  92     x *= Math.pow(2, 1023);
  93     if (exp > 1023) {  // in case x is subnormal
  94       exp -= 1023;
  95       x *= Math.pow(2, 1023);
  96     }
  97   }
  98   if (exp < -1023) {
  99     exp += 1023;
 100     x *= Math.pow(2, -1023);
 101   }
 102   x *= Math.pow(2, exp);
 103   return x;
 104 }
 105 //Provides: caml_frexp_float const
 106 function caml_frexp_float (x) {
 107   if ((x == 0) || !isFinite(x)) return [0, x, 0];
 108   var neg = x < 0;
 109   if (neg) x = - x;
 110   var exp = Math.floor(Math.LOG2E*Math.log(x)) + 1;
 111   x *= Math.pow(2,-exp);
 112   if (x < 0.5) { x *= 2; exp -= 1; }
 113   if (neg) x = - x;
 114   return [0, x, exp];
 115 }
 116
 117 //Provides: caml_float_compare const
 118 function caml_float_compare (x, y) {
 119   if (x === y) return 0;
 120   if (x < y) return -1;
 121   if (x > y) return 1;
 122   if (x === x) return 1;
 123   if (y === y) return -1;
 124   return 0;
 125 }
 126
 127 // FIX: these four functions only give approximate results.
 128 //Provides: caml_log10_float const
 129 function caml_log10_float (x) { return Math.LOG10E * Math.log(x); }
 130 //Provides: caml_cosh_float const
 131 function caml_cosh_float (x) { return (Math.exp(x) + Math.exp(-x)) / 2; }
 132 //Provides: caml_sinh_float const
 133 function caml_sinh_float (x) { return (Math.exp(x) - Math.exp(-x)) / 2; }
 134 //Provides: caml_tanh_float const
 135 function caml_tanh_float (x) {
 136   var y = Math.exp(x), z = Math.exp(-x);
 137   return (y + z) / (y - z);
 138 }