mpf_pow.c

   1 /* LibTomFloat, multiple-precision floating-point library
   2  *
   3  * LibTomFloat is a library that provides multiple-precision
   4  * floating-point artihmetic as well as trigonometric functionality.
   5  *
   6  * This library requires the public domain LibTomMath to be installed.
   7  *
   8  * This library is free for all purposes without any express
   9  * gurantee it works
  10  *
  11  * Tom St Denis, tomstdenis@iahu.ca, http://float.libtomcrypt.org
  12  */
  13 #include <tomfloat.h>
  14
  15 /* we have e^x, so why not write a^b as e^(lna * b) ;-) w00t w00t */
  16 int  mpf_pow(mp_float *a, mp_float *b, mp_float *c)
  17 {
  18    mp_float  exponent;
  19    int       err;
  20
  21    if ((err = mpf_init(&exponent, c->radix)) != MP_OKAY) {
  22       return err;
  23    }
  24
  25    /* get ln of a */
  26    if ((err = mpf_ln(a, &exponent)) != MP_OKAY)                      { goto __ERR; }
  27
  28    /* multiply it by b */
  29    if ((err = mpf_mul(&exponent, b, &exponent)) != MP_OKAY)          { goto __ERR; }
  30
  31    /* now evaluate it */
  32    err = mpf_exp(&exponent, c);
  33
  34 __ERR: mpf_clear(&exponent);
  35    return err;
  36 }