Mixed int/BigInt foreach interval

[Jonathan M Davis]

On Monday, September 26, 2011 13:47 Paul D. Anderson wrote:
> bearophile Wrote:
> > Time ago I've asked to use BigInt with iota too (no D changes needed
> > here): http://d.puremagic.com/issues/show_bug.cgi?id=6447
> 
> > because currently this doesn't work (std.traits.isIntegral needs to 
change, and there changes needed in iota too, because it can't use the current 
std.traits.unsigned, because a BigInt has no ".min" field):
> Yes, it would be nice to allow isIntegral, isArithmetic, etc. to recognize
> library types and not just built-in types.
> 
> This would be helpful for, for instance, rational numbers and decimal
> numbers (BigDecimal and decimal32, decimal64, decimal128.
> 
> As an aside, for those who are interested, the Decimal library implementing
> the numbers listed above is very near completion. Just some testing and
> tidying to do before it can go on the review queue.

I think that we need to be _very_ careful about the implications of making 
isIntegral and other similar traits functions work with non-primitive types. 
There could _easily_ be code which assumes that it's going to get primitive 
types when isIntegral is true. Take the integer swapping code in std.bitmanip. 
It would fail miserably if all of a sudden BigInt worked with isIntegral, and 
you tried to use BigInt with it.

I can see we might want to have isIntegral work with BigInt, but I do _not_ 
think it's necessarily the case that it's actually a good idea. We need to be 
careful about the implications of all of that and make very informed decisions 
about the changes that we make to std.traits, or a lot of code is going to 
break in non-obvious ways.

- Jonathan M Davis