On Wednesday, January 17, 2024 7:55:37 PM MST zjh via Digitalmars-d-learn wrote:
> Can you change the type of 'length' from 'ulong' to 'int', so I haven't to convert it every time!

If you mean for arrays, length and array indices are specifically size_t so that their size will match the pointer size for the architecture. On 64-bit systems, that means that it's ulong (whereas on 32-bit systems, it would be uint). If it were int, then you couldn't access all of the elements of larger arrays (and arrays will get that large in some cases - e.g. when dealing with larger files). C/C++ does the same thing.

If you want your code to be portable and to be able to handle larger arrays, then it should be using size_t for array indices and length and not int, in which case, you're not typically going to need to convert from ulong to int, because you'd just be using size_t, which would then be ulong on 64-bit systems. Obviously, when you do need to convert to int, then that can be annoying, but for a lot of code, using auto and size_t makes it so that you don't need to use int, and it would be a big problem in general if the language made length int.

- Jonathan M Davis

On Wednesday, January 17, 2024 11:33:48 PM MST zjh via Digitalmars-d-learn wrote:
> On Thursday, 18 January 2024 at 04:30:33 UTC, Jonathan M Davis
> wrote:
> but for a lot of code, using auto and size_t makes it
>
> > so that you don't need to use int, and it would be a big problem in general if the language made length int.
>
> It's hard to imagine that an `'int'` needs to be replaced with `'auto'`.

It's very common in D code to do stuff like

auto a = foo();

or

auto len = arr.length;

That way, you automatically get the correct type. Obviously, there are cases where you need to force a particular type, and that can require casting, but inferring types often simplifies code. It's _very_ common in idiomatic D code to use auto when you don't need to force a specific type. And when dealing with arrays, it's very typical to use either auto or size_t, because then you get the correct integer type regardless of the platform, and then you only need to worry about casting to int in cases where you actually need int for whatever reason.

But regardless of whether you want to use auto, there are very good reasons for why length is size_t, and C/C++ made exactly the same choice for the same reasons. You can certainly disagree with that choice, but it's not the kind of thing that stands much chance of ever being changed.

- Jonathan M Davis