[uint] conversion between uint types

[wojciech-cichocki]

Is there an existing issue?

• I have searched the existing issues. There is no such request yet, but here's a request with the most similar vibe: uint: add casting from/to U64 #691

Experiencing problems? Have you tried our Stack Exchange first?

• This is not a support question.

Question:
What is recommended way to convert one type of uint to another?

Background:
I've developed a high-level lib for creating custom DeFi-oriented types that are implemented in pure Rust, where uint types serve as underlying types.

Details:
In certain scenarios, I need to expand the type to prevent overflow in intermediate calculations. For instance, there are cases where I must extend the type from U256 to U512. I'm exploring the best approach to convert between different uint types.

Based on my observations, it seems that try_from is only implemented for primitive types. One option is to manually rewrite the u64 values, but I believe there might be a more elegant solution. Perhaps it's worth considering the addition of a try_from implementation for converting between types at the uint library level.

As an illustration, consider the following two types:

construct_uint! {
    pub struct U256(4);
}

construct_uint! {
    pub struct U512(8);
}

In this context, creating a U512 type based on a U256 instance could look like this:

U512::try_from(U256::MAX)

Are you willing to help with this request?
I am willing to create a proposal for implementation if the feature is deemed useful.

[ggwpez]

U512::try_from(U256::MAX)

In this case the the conversion is always infallible, so why the try?
I am not sure what exactly you need, but if its just conversion methods then sure we can use those 😄

Just FYI we also have fixed point math in Substrate: https://paritytech.github.io/polkadot-sdk/master/sp_arithmetic/index.html

[wojciech-cichocki]

I meant a generic conversion between any types of uints, so try can be useful if the value doesn't fit. What's more, uint dependency is required in my case.