Implement Pow for BigUint and BigInt

[clarfonthey]

See rust-num/num-traits#38 for details on this trait.

[vks]

Is this necessary given that it is implemented in num-traits now?

[cuviper]

What do you mean? Pow is defined in num-traits, and implemented for the primitive types, but we need to implement it here for bigints.

[vks]

I thought num-traits provided a generic implementation, but apparently that is not the case.

[thomwiggers]

Let's see if I can do this – I need in anyhow.

[vks]

@cuviper I found it: num_traits::pow. This should work for BigInt as well. (Something like powm in this num-integer PR would probably be more efficient though.)

[cuviper]

I found it: num_traits::pow. This should work for BigInt as well.

Yes, but that only works by-value with a usize exponent. The Pow trait is more flexible.

(Something like powm in this num-integer PR would probably be more efficient though.)

Modular pow is a different thing though -- and FWIW we do have inherent modpow methods here.

[vks]

Yes, but that only works by-value with a usize exponent. The Pow trait is more flexible.

A u32 exponent should be enough, and by-value is more efficient.

[windelbouwman]

I'm interested in this pow function, will there be a new release of this crate at some point containing pow, or is there work left to do?

[cuviper]

Thanks for the reminder - I've published num-bigint 0.2.1.