C随机范围内的数字

//改编自lua的math.random函数#include <stdio.h>#include <stdlib.h>#include <math.h>#include <time.h>            #define RAND_MAX 2147483647#define lua_Number double            int math_random(int down_limit, int up_limit){               lua_Number r = (lua_Number)(rand() % RAND_MAX) / (lua_Number)RAND_MAX;                lua_Number l = down_limit;    lua_Number u = up_limit;                lua_Number ret = floor(r * (u - l + 1 ) + l);                 return (int)ret;}                       int main(int argc, char* argv[]){               srand(time(NULL));    printf("RAND_MAX %d\n", RAND_MAX);                            int i = 0;    for (i = 0; i < 100; ++i) {        int ret = math_random(-3, 3);printf("%d\n", ret);                                }                       return 0;}