On 2012-09-17 18:34, monarch_dodra wrote:
I love D's concept of arrays (fat pointers).

However, one thing I've found it lacks is a (convenient) way to get the
end ptr.

Phobos (and druntime) are riddled with "arr.ptr + arr.length". It is
ugly and inconvenient, and makes something that should be easy to
understand that much harder.

Then I thought: "std.array" defines all the functions required to
enhance arrays. Why not just add a "ptrEnd" in there? So I did.

The rational is that now, we can write:

bool isDisjoint = a.ptrEnd <= b.ptr || b.ptrEnd <= a.ptr;

More elegant than:

bool isDisjoint = a.ptr + a.length <= b.ptr ||
                   b.ptr + b.length <= a.ptr;

Nothing revolutionary, but it *is* easier on the fingers when typing :D
. Also, it *does* make a change in some bigger and more complicated cases.

Anyways, pull request:
https://github.com/D-Programming-Language/phobos/pull/798

I wanted to have some feedback, as this is introducing something new (as
opposed to fixing something existing).

IMO, this should really be built-in, in particular, since, in my
understanding, an array is internally represented by the ptr and ptrEnd
pair anyways. If the compiler has access to it, it might as well
communicate it (rather than us re-calculating it...)

Rather than adding new language features we're moving stuff out of the core language and into the runtime/standard library. This is a perfect example of a library function. Since we have UFCS it would behave and look exactly the same as if it was a built-in property on arrays. If this is added to the "object" module in druntime you wouldn't even need to import anything.

--
/Jacob Carlborg

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