std.range.iota enhancement: supporting more types (AKA issue 10762)

[H. S. Teoh]

On Tue, Dec 24, 2013 at 09:10:53AM -0800, Andrei Alexandrescu wrote:
> On 12/24/13 5:09 AM, Joseph Rushton Wakeling wrote:
> >On 24/12/13 13:58, monarch_dodra wrote:
> >>I think you are missing the point of what happens if the step is not
> >>1 (or if the passed in type can have fractional input). EG:
> >>
> >>iota(0, 105, 10);
> >>or
> >>iota(0, 10.5);
> >>
> >>In this case, "back" should be 100, and not 95. To compute back, you
> >>need to be able to evaluate length, and to add length*inc to front.
> >
> >Oh, snap.  Have we been working on the same problems for too long?
> >:-)
> 
> The integral cases are easy. We need to crack the floating point case:
> given numbers low, up, and step, what's the closest number smaller
> than up that's reached by repeated adds of step to low?
[...]

The closest number is simply step*floor((up-low)/step). There's probably
a better way to write that expression that avoids bad roundoff errors,
though.


T

-- 
Why can't you just be a nonconformist like everyone else? -- YHL