RFC on range design for D2

[Bruno Medeiros]

Andrei Alexandrescu wrote:
> Lars Ivar Igesund wrote:
>> Andrei Alexandrescu wrote:
>>
>>> A slice is a range alright without any extra adaptation. It has some
>>> extra functions, e.g. ~=, that are not defined for ranges.
>>
>> Aren't slices const/readonly/whatnot and thus ~= not possible without
>> copying/allocation?
> 
> Well there's no change in semantics of slices (meaning T[]) between D1 
> and D2, so slices mean business as usual. Maybe you are referring to 
> strings, aka invariant(char)[]?
> 
> Anyhow, today's ~= behaves really really erratically. I'd get rid of it 
> if I could. Take a look at this:
> 
> import std.stdio;
> 
> void main(string args[]) {
>     auto a = new int[10];
>     a[] = 10;
>     auto b = a;
>     writeln(b);
>     a = a[1 .. 5];
>     a ~= [ 34, 345, 4324 ];
>     writeln(b);
> }
> 
> The program will print all 10s two times. But if we change a[1 .. 5] 
> with a[0 .. 5] the behavior will be very different! a will grow "over" 
> b, thus stomping over its content.
> 
> This is really bad because the behavior of a simple operation ~= depends 
> on the history of the slice on the left hand side, something often 
> extremely difficult to track, and actually impossible if the slice was 
> received as an argument to a function.
> 
> IMHO such a faux pas is inadmissible for a modern language.
> 
> 
> Andrei

Cool, good to see this is going to be taken care of, it is a horrible wart.


-- 
Bruno Medeiros - Software Developer, MSc. in CS/E graduate
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D