11.12.1 ProblemWhen looking for a random floating-point number, we usually want a value between 0 and 1 that is just as likely to be between 0 and 0.1 as it is to be between 0.9 and 1. 11.12.2 SolutionBecause of the way that floating-point numbers are stored, simply casting bits to a float will make the distribution nonuniform. Instead, get a random unsigned integer, and divide. 11.12.3 DiscussionBecause integer values are uniformly distributed, you can get a random integer and divide so that it is a value between 0 and 1: #include <limits.h> double spc_rand_real(void) { return ((double)spc_rand_uint( )) / (double)UINT_MAX; } Note that to get a random number between 0 and n, you can multiply the result of spc_rand_real( ) by n. To get a real number within a range inclusive of the range's bounds, do this: #include <stdlib.h> double spc_rand_real_range(double min, double max) { if (max < min) abort( ); return spc_rand_real( ) * (max - min) + min; } |