Lets deprecate the length in the arrays index

[Lionello Lunesu]

Frank Benoit (keinfarbton) wrote:
> There was this thread:
> 
> 22-Oct-2005
> It's time to deprecate "array [length]" in favour of "array [$]"
> 
> Actually I noticed, i still can use length inside an array index, even
> if compiling without -d (deprecated).
> 
> For me that means, I do not use the identifier 'length' in D. For
> nothing. Because it can happen, it collides with this array stranger.
> 
> Please remove this or deprecated this.

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.