impl std::error::Error for rand_distr::*Error.

[kennytm]

Also re-exported BernoulliError into rand_distr.

[burdges]

Requires feature gates for std.

I wrote posted some thought about an error trait without alloc btw:
rust-lang/rfcs#2820 (comment)

[kennytm]

@burdges rand_distr does not have a gate for std because it uses std-only methods like f64::powi (see rust-lang/rfcs#2505).

Unlike most Rand crates, rand_distr does not currently support no_std.

Until we get non-std-support of these math functions there's no point to feature gate std::error::Error.

[dhardy]

Could you add a note to the changelog please? https://rust-random.github.io/book/contributing.html#pull-requests

[dhardy]

Thanks; mostly this looks good but perhaps a couple of doc strings should be tweaked.

[dhardy]

Looks good.

Sorry to add yet another thing to this PR, but I just realised we don't catch the Bernoulli::new(NaN) case. I don't think this is classified as a breaking change, but is worth a mention in the changelog. Can I get you to add it to this PR? Thanks.

[dhardy]

That also applies to from_ratio(0, 0). Okay, this is technically a different change, so should be a different PR.