Range Type

bobcat a at b.com
Mon Mar 24 19:52:18 PDT 2008


Nice! I was also wishing for ranges in D, but didn't know how it would behave with the rest of the languages. 
Doing foreach(i, 1..20) would also be a natural fit for this, where foreach also accepts a slice :). ( I know there is already something similar in D 2.0. )

Janice Caron Wrote:

> I know this has cropped up before (in discussions about multiple
> dimension arrays), but adding a range type would also really help with
> the whole business of returning slices. (See the many other threads
> currently buzzing with this topic).
> 
> A range is nothing more than a two-element struct
> 
>     struct Range(T,U=T)
>     {
>         T begin;
>         U end;
>     }
> 
> However, if you throw in some extra language support, it gets really,
> really useful. Basically, you want the ".." infix operator always to
> create a range. Thus
> 
>     auto x = 3 .. 4;
> 
> creates a Range!(int) with values { 3, 4 }. In general (a .. b) should
> evaluate to a Range!(typeof(a),typeof(b)) with values { a, b }.
> Finally, you also want [] and opSlice() to accept Range! parameters,
> so that
> 
>     s = s[a..b];
> 
> can always be rewritten as
> 
>     auto t = a..b;
>     s = s[t];
> 
> In general, opSlice(Range r) should be eqivalent to opSlice(r.begin, r.end).
> 
> In my opinion language support for ranges (allowing .. to return a
> range, and allowing [] to accept a range) has advantages above and
> beyond those already discussed, and may also allow many other exciting
> possibilites we haven't even thought of yet.




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