Lets deprecate the length in the arrays index

[janderson]

Lionello Lunesu wrote:
> Frank Benoit (keinfarbton) wrote:
>> There was this thread:
>>
> 
> I'd like the special case "length" to be removed as much as the next 
> guy, but actually, I think it would be nicer to generalize it: why not 
> let the brackets [..] be treated as an implicit with()? I mean, inside 
> the brackets you have the context of the thing before the brackets:
> 
> array[identifier];
> //=>
> with(array)
>   opIndex(identifier);
> //and
> array[ident1..ident2];
> //=>
> with(array)
>   opSlice(ident1,ident2);
> 
> (ATM, 'with' only accepts class objects)
> 
> This gets rid of the special case and makes it available to class object:
> 
> import std.stdio;
> class X {
>     uint length;
>     char[] opIndex(uint x) { return "index"; }
>     char[][] opSlice(uint f,uint t) { return ["op","slice"]; }
> }
> void main()
> {
>     auto x = new X;
>     writefln(x[length-1]);    // now needs x.length
>     writefln(x[0..length-1]); // now needs x.length
>     writefln(x[$-1]);
>     writefln(x[0..$-1]);
> 
>     with(x) {
>         writefln( opIndex(length-1) );
>         writefln( opSlice(0,length-1) );
>         int length = 23;      // compiler does not complain :(
>     }
> }
> 
> Note that if X were to have a member "uint first", I would be able to do 
>  "x[first]".
> 
> Ideally, the compiler would complain if an ambiguous symbol was being 
> used inside with (and [], [..]).
> 
> L.

Gotta say I like this idea.  It would make code more manageable if you 
could do things like:

char[] value = line[find('a')+1..find_r('b')];

instead of,

char[] value = line[line.find('a')+1..line.find_r('b')];

Although in something like the above you'd want to make sure that both a 
and b exist before doing these searches.  Playing the D advocate for a 
second, maybe we don't want to encourage this style of coding?

-Joel