How to convert from a smaller type to a larger one? (e.g. U256 to U320)

[dEajL3kA]

Hello.

As the title says, I need to convert from a smaller type (e.g. U256) to a larger type (e.g. U320).

What is the recommended way to do this?

It appears that neither U320::from() nor U320::try_from() nor U320::new() can do this out-of-the-box 😕

I have come up with the following solution, but I'm not sure it's the "best"™ way to go?

fn convert(value: U256) -> U320 {
	let mut words = [Word::ZERO; U320::LIMBS];
	words[..U256::LIMBS].copy_from_slice(value.as_words());
	U320::from_words(words)
}

Thanks for any advice!

[tarcieri]

The main built-in methods are the Concat and ConcatMixed traits.

We could potentially add inherent methods for this as well. BoxedUint has Resize

[dEajL3kA]

Thanks. Didn't realize ConcatMixed and SplitMixed can do the required conversions to/from a smaller/larger size 😎