Great code! I would extract the internal lambda into a separate function, but otherwise the solution is simply brilliant and most importantly, readable and clear. Good job! 👏👏

the return type does not even matter here. two integers that hold the same value will always compare equal, no matter their respective bit-width and signedness:

(signed char)123 == (unsigned long long)123

I feel extremely dumb with my char cast hahahaha

Please use spoiler flag next time, your post was visible in the homepage.

In Dart 3 break is not required. default is optional.

Why you dont need break in each case and a default block?

Agda Translation

😄

I completely missed a < b in the constraints section. It is better to specify a < b in the first sentence: "You are given positive integers, a and b, a < b".

dude, it's specified

The description should specify that a != b. Moreover, in all tests a < b. If it is intentional then it should be specified.

More modules should be banned (see this solution).

Val and App have been replaced with Value and Apply where appropriate.

Expr and Op now derive Eq. There really isn't a natural ordering of the arithmetic operations, so I've held off on deriving Ord. Solvers are free to derive their own if they wish.