feat(smt): add smt crate

[waddaboo]

Description

Added the Sparse Merkle Tree (SMT) implementation in Rust.

Related Issue(s)

Closes: #8

Other information

• Please do let me know if anything can be improved.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have run yarn format and yarn compile without getting any errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Additional Questions

• Need to add actual hash functions to test?

[sripwoud]

tACK

Thanks @waddaboo
Nice you added docstring and a README.

I

• checked tests locally
• checked the function signatures and overall code to see if it matches the original TS implementation

I suggested some improvements but they aren't blocking merging this PR imo

Let's wait for someone else review too cc @curryrasul
Don't forget to format the code in order to have the ci check pass

[sripwoud]

do you think this should be included in the published crates?
If not we need to add an exclude or include field to the crate's manifest

[waddaboo]

Thanks for the review!

I saw some other libraries included examples and some did not, so I'm not sure either. Since the README Usage section is the same as in examples, I think it's ok to remove it?

[sripwoud]

I like adding the flexibility of working with String or BigInt.

What do you (and other reviewers) think of using generics instead?

[0xjei]

Yes, it might make sense to avoid doing these checks at runtime, but 90% of things can be represented by String and BigInt. I don't know if the game is worth the candle. Anyone has any additional comments here?

[sripwoud]

see previous comment, wouldn't it be nicer to rely on generics instead of making a runtime check on big_numbers?

I am thinking about something like:

pub struct SMT<T>  
where
    T: Clone + PartialEq + Eq + Hash + Display + FromStr {}

pub enum Node<T>
where
    T: Clone + PartialEq + Eq + Hash + Display + FromStr,
{
    Value(T),
}

impl<T> SMT<T> {}


let smt_string = SMT::<String>::new(hash_function);
let smt_bigint = SMT::<BigInt>::new(hash_function);

[sripwoud]

let's not block that PR based on my previous comment. My comment on generics probably apply to the TS implementation too.
And this PR should mirror the TS implementation, which is does 👌

[0xjei]

tACK - thank you @waddaboo the code looks polished and precise. I don't have additional comments beside the @sripwoud ones.

[waddaboo]

@0xjei Thanks for the review! As for the comment on using generics, do I implement it now or wait for further comments?

[sripwoud]

@0xjei Thanks for the review! As for the comment on using generics, do I implement it now or wait for further comments?

No need to implement it now.

Let's merge. @cedoor we need your approval too.
@curryrasul can make post merge comments. If necessary we ll implement other requests for changes later.

Thanks @waddaboo

[cedoor]

@sripwoud thanks. Ready to be merged 👍🏽