When to use iarray instead of array?

[otini]

@jbe

And indeed, those are part of OCaml 5.4: module IArray and also a type iarray (for which I don’t seem to find an entry in the manual here; maybe it is missing in the manual?).

The intention is that people should rather use Iarray.t, and iarray is a built-in type that is more an implementation detail that may disappear from the interface. (In fact, we should rewrite this API to expose 'a Iarray.t rather than 'a iarray).

@jbe

I don’t want the function to modify/destroy the input arguments. So I assume changing my function to accept an iarray is fine? But while I’m calculating the output, as a last step of the Gauss algorithm, I keep the numbers in a mutable array anyway. So is it reasonable to return that mutable array instead of converting it into an immutable array? (Afterall, some future users of my function might want to modify the result.)

Or should I stick to one kind of array and use it consistently for input and output?

The intention of immutable arrays is mostly to have better APIs: documenting that functions do not modify their arguments for instance.

So it’s up to you and to how you think your API should be used. If it’s convenient for your users to be able to modify the result of a function, maybe you should use a mutable array.

@jbe

But while I’m calculating the output, as a last step of the Gauss algorithm, I keep the numbers in a mutable array anyway.

Note that Dynarray.unsafe_to_iarray exists, i.e., turning a mutable (and dynamically-sized) array to an iarray without a copy (under some conditions).

@jbe

Also note that there doesn’t seem to be an Alcotest.iarray, so I have to convert my iarray first to an array before Alcotest is able to process it. Either by providing a corresponding testable as above, or by manually converting all iarrays into array before letting Alcotest process them.

Since Iarray.t is in the stdlib, I think it would make sense to suggest to the alcotest maintainers to add Alcotest.iarray.