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

[Andrei Alexandrescu]

On 12/24/13 10:56 AM, Craig Dillabaugh wrote:
> On Tuesday, 24 December 2013 at 17:10:53 UTC, 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?
>>
>> Andrei
>
> Doesn't think work, or am I missing something?
>
> low + floor( (up-low)/step ) * step

I doubt it's anything as simple as that. The magnitudes of up, low, and 
step must be taken into account.

Andrei