On Tuesday, 2 October 2012 at 18:45:24 UTC, David Nadlinger wrote:
On Tuesday, 2 October 2012 at 17:24:32 UTC, Andrei Alexandrescu
wrote:
Yes. Unfortunately there are few, few cases in which size_t is
insufficient (e.g. an input range from a file or a large iota,
both on 32-bit builds). I personally think these are too few
to need formal support.
I'd throw bit arrays into the mix, where 32 bit can also be
quite small. There might also be some other clever hacks using
custom index types for representing non-linear data structures
as ranges.
The question is whether such ranges are likely to be used as
random access ranges. I can't come up with a compelling use
case right now, but I'd rather think twice before throwing
support for them out of the window and later regretting it.
Also, one of the simplest ranges (iota) not fitting the range
concept has somewhat of an odd aftertaste.
It's easy to think of random access ranges that could easily need
more than size_t:
- The cartesian product of several smaller ranges
- a permutationsOf(r) range
- a subsetsOf(r) range
Any combinatoric range would easily use up 32-bit and 64-bit
indexing. If 32-bit sometimes isn't enough, then neither is
64-bit.
So, the question is, do we want to allow the use of BigInt
indexing?
