Replace functor IntervalFunctor with a module

[jerhard]

Currently, the IntervalFunctor takes an IntOps module to allow instantiations of the interval domain to work with either int64 or bigints. The only places that still rely on the intervals using int64 internally are the ranges for DefExc and Enums, but these can be patched to work with bigints.

A benefit would be that the code structure gets simpler by getting rid of the functor, and additionally, the functions in IntDomain.Size would work on bigints more uniformly.

[sim642]

The only places that still rely on the intervals using int64 internally are the ranges for DefExc and Enums, but these can be patched to work with bigints.

But these ranges represent the number of bits, not the values themselves, right? Seems way overkill to use bigints for numbers like 64 or -63.
Tbh, it'd make even more sense to switch them from int64 to int (which Size.bits returns anyway without problem), which has even less memory overhead in the OCaml runtime.

A benefit would be that the code structure gets simpler by getting rid of the functor

Does it actually get simpler by any extent? First, you just get rid of the functor's argument and hardcode module Ints_t = IntOps.BigIntOps. Second, you could inline all the Ints_t calls, but I'd argue it's not any easier to read Big_int_Z.add_big_int instead of Ints_t.add, etc.

the functions in IntDomain.Size would work on bigints more uniformly.

I suppose you're referring to the fact that many of them still return int64s, but also have bigint returning versions. Surely the int64 versions could be removed and the places that still depend on that can simply use IntOps.of_bigint at their own risk of erroring (which happens currently anyway as Size raises Not_in_int64 in some cases).

So given the generality of the already implemented functor, I don't really see the reason to throw it away. Especially now that in #251 the flattened int domain has also been generalized to any IntOps.

I think there are other parts of IntDomain that are a much bigger source of confusion

[vogler]

But these ranges represent the number of bits, not the values themselves, right? Seems way overkill to use bigints for numbers like 64 or -63.
Tbh, it'd make even more sense to switch them from int64 to int (which Size.bits returns anyway without problem), which has even less memory overhead in the OCaml runtime.

Agree

the functions in IntDomain.Size would work on bigints more uniformly.

I suppose you're referring to the fact that many of them still return int64s, but also have bigint returning versions. Surely the int64 versions could be removed and the places that still depend on that can simply use IntOps.of_bigint at their own risk of erroring (which happens currently anyway as Size raises Not_in_int64 in some cases).

I thought they only return big_int where needed, and use int or int64 for number of bits etc.
The code was written at a time when all int domains used int64 instead of big_int.
So, yes, some cleanup there would prob. be better.

[michael-schwarz]

What is the state here? Do we still want to do this, or should we close the issue?

[sim642]

My opinion is still that it should remain as a functor. In the light of #734 it might even be beneficial to further extract and generalize the interval domain, such that certain parts could be reused for floats as well.

[jerhard]

I closed the issue as there are still two instances of the functor (with bigints and with 64 bit-ints).