rand(num) won't work with big_ints

[jzakiya]

crystal 0.24.1

translating code from Ruby and hit this bug when doing

rand(self-4)  

when self is big_int

[oprypin]

Hi,
I'll try to explain the lack of response:
This is a valid feature request but probably very low priority.

In most cases you can work around this by getting a random Int64 or Float64 first

[jzakiya]

The hack below at least got the code to compile, but it's sooooo ugly, and probably doesn't have the statistical properties of a real random distribution.

b = 2 + ((self-4).to_f * Random.rand).to_big_i

[iSarCasm]

Hello. What is the best way to implement random for BigInts @ysbaddaden ? There is some random inside GMP or should I just dance with Random::Secure.next_u?
https://github.com/crystal-lang/crystal/blob/master/src/random.cr
https://github.com/crystal-lang/crystal/blob/master/src/random/secure.cr
Thanks

[oprypin]

If covering all possible values is not critical, you can work around this with rand(range : Range(Float, Float)) : Float and rounding.

[oprypin]

And the proper solution would be extending the algorithm to support BigInt (shouldn't be too hard)

[iSarCasm]

@oprypin Yes, I need the whole range for the cryptographic algorithm. Thanks, I will try to extend this alg.