1  /* Test of modf*() function family.
       2     Copyright (C) 2012-2022 Free Software Foundation, Inc.
       3  
       4     This program is free software: you can redistribute it and/or modify
       5     it under the terms of the GNU General Public License as published by
       6     the Free Software Foundation, either version 3 of the License, or
       7     (at your option) any later version.
       8  
       9     This program is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      12     GNU General Public License for more details.
      13  
      14     You should have received a copy of the GNU General Public License
      15     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      16  
      17  static void
      18  test_function (void)
      19  {
      20    int i;
      21    const DOUBLE TWO_MANT_DIG =
      22      /* Assume MANT_DIG <= 5 * 31.
      23         Use the identity
      24           n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5).  */
      25      (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
      26      * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
      27      * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
      28      * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
      29      * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
      30  
      31    /* Randomized tests.  */
      32    for (i = 0; i < SIZEOF (RANDOM); i++)
      33      {
      34        DOUBLE x = RANDOM[i]; /* 0.0 <= x < 1.0 */
      35        DOUBLE y;
      36        DOUBLE z;
      37  
      38        y = MODF (x, &z);
      39        ASSERT (z == L_(0.0));
      40        ASSERT (y == x);
      41  
      42        y = MODF (- x, &z);
      43        ASSERT (z == L_(0.0));
      44        ASSERT (y == - x);
      45  
      46        y = MODF (L_(1.0) + x, &z);
      47        ASSERT (z == L_(1.0));
      48        y -= x;
      49        ASSERT (y >= - L_(1.0) / TWO_MANT_DIG);
      50        ASSERT (y <= L_(1.0) / TWO_MANT_DIG);
      51  
      52        y = MODF (- L_(1.0) - x, &z);
      53        ASSERT (z == - L_(1.0));
      54        y -= - x;
      55        ASSERT (y >= - L_(1.0) / TWO_MANT_DIG);
      56        ASSERT (y <= L_(1.0) / TWO_MANT_DIG);
      57      }
      58  }
      59  
      60  volatile DOUBLE x;
      61  DOUBLE y;
      62  DOUBLE z;