How can i create function in C , which would generate random number }(type double) between set arguments? In lot of languagues its simply just
function randomnumber(min, max) {
return Math.random() * (max - min + 1) + min;
}
but i fail to find any good solution for type double in c.
There are several methods. Answer 1 above is ok for min, max as doubles. The important thing to remember for rand() is that it returns a random integer between 0 and RAND_MAX inclusive. RAND_MAX is a least 2^15, but on most systems 2^31. If min and max are integers and their difference is less than RAND_MAX then a very easy method is:
delta = max - min;
r = rand() % delta + min;
#include <stdlib.h> /* rand(), srand(), RAND_MAX */
double randd(double min, double max) {
int r = rand();
double delta = max - min; /* assume max > min */
double tmp = r / (RAND_MAX + 1.0); /* generate up to but excluding max */
return tmp * delta + min;
}
double between min and max.min and max this answer, with its bias, can generate every double between those values .... and repeat some of the answers to boot (think 52 bits for the mantissa and 63 bits for the PRNG).int of 63+ bits - the return type of rand() - more likely to be 32-bit (or even 16) and so insufficient to generate all the range of double with many min, max. Had this answers referenced a 63 bit PRNG or express how to compensate for insufficient RAND_MAX range, I would have not commented so.
floorso you really want a random integer?function...? :) return type? type of arguments?float, yet the post requestdouble. That extra precision/range poses additional concerns that a good answer would provide.maxandmin? It is easier to not include one of the limits so like[min...max)rather than[min... max]. Do you want to be able to generate everydoublebetweenminandmaxor just most of them sufficient?