Creating a custom iota()

[H. S. Teoh]

On Thu, May 12, 2022 at 11:57:54AM +0000, realhet via Digitalmars-d-learn wrote:
[...]
> I have my own DateTime struct.
> It has opCmp() and opBinary(), I can do arithmetic with this custom
> DateTime and the amazing time units of the **quantities** package.
> 
> Now I'm about mo make iterations in a DateTime range:
> 
>     const
>       st = DateTime(UTC, "22.1.1 8:30").utcDayStart,
>       en = DateTime(UTC, "22.3.5 19:56").max(now).utcDayStart +
> (100.0/64)*nano(second);
> 
>     //this works
>     for(auto d = cast()st; d < en; d += day) writeln(d);
> 
>     //this would be nicer, but not works
>     iota(st, en, day).each!writeln;
> 
> My question is, is there a way to 'extend' the functionality of the
> std.iota() function or it is better to come up with a unique name for
> this special 'iota' functionality?

Custom user types should already be supported by iota; see:

	https://issues.dlang.org/show_bug.cgi?id=10762

Does your DateTime type support the `++` operator?  If not, that's the
most likely reason iota failed to instantiate on it.  Just add
`opUnary(string op : "++")` to your type, and it should work.


[...]
> Or maybe put it inside a DateTimeRange struct, and implement the std
> range functionality?
[...]

That would work too.

But I'm curious, why didn't you use std.datetime?  The DateTime type
there supports inter-date arithmetic (as far as it makes sense), and can
be easily made into a range using std.range.recurrence.


T

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