Hint ite statements

[0xnullifier]

@katat I think I could not explain things in the issue so I have raised a draft pull request. For the example of if_else.no taken in the pr it works as the blocks early returns but if I change the example to something like this:

hint fn ite(xx: Field , arr: [Field;LEN]) -> Field {
    let mut var = 0;
    if xx == 10 {
        var = xx;
        for idx in 0..LEN {
            var = var + arr[idx];
        }
        var = xx * var;
    } else {
       var = xx * xx;
    }
    return var;
}

this causes the then_branch return type to panic. So how can I support these type of statements? moreover what about only if statements?

[katat]

The reason it panics is the example you provided returns none for the ITE branches.

Let's first agree on the grammar on this enhanced ITE statement.

I would suggest to still align with the grammar supported in the constraint code:

let res = if cond {t1} else {t2};

In hint function for now, we would just add the support of return statement.

In your example, we would instead enforce it to be:

hint fn ite(xx: Field , arr: [Field;LEN]) -> Field {
    let mut var = 0;
    let res = if xx == 10 {
        var = xx;
        for idx in 0..LEN {
            var = var + arr[idx];
        }
        xx * var // align with the existing grammar
    } else {
       return xx * xx // or it returns
    }
    return res;
}

This way aligns with the existing grammar in constraint mode, while avoiding adding too much complexity for this enhancement at this stage.

[katat]

why then_branch block isn't handled the same way as the else_branch block?

[katat]

shouldn't the fn_env.nest() and fn_env.pop() be called for each compile_block?

[0xnullifier]

@katat hey sorry for the delay I am a little busy with some work this week. I will pick this up again after the weekend