Implement rand traits for Ratio ?

[pwnorbitals]

I'm especially interested in the implementation of Distribution<num::Ratio> for Standard and the UniformSampler backend to use gen_range() on custom types that wrap num::Ratio

[cuviper]

Do you know how to actually achieve a uniform sample with a ratio? I think that's not easy, unless you just pick a specific denominator and then uniformly randomize the numerator. Is there a better way?

[clarfonthey]

I agree with cuviper -- I'm not 100% sure uniform randomness inside a range for Ratio is something that can be easily quantified. Most people will have their own idea of how the algorithm should work, and mathematically it's not really well-founded since all definitions of probability rely on real numbers, which can't easily be approximated with ratios. In the absolute case, if you wanted to generate a random Ratio<BigInt>, I don't think that it'd be desirable that there's a chance that the numerator and denominator can be arbitrarily large.

The only solution that makes sense to me is to just randomly generate a float and then convert that to a ratio to whatever precision you want. Which, can easily be accomplished by doing… just that.