in operator generalization

[Stewart Gordon]

Les Baker wrote:
> Looking through old NG posts I found this one by Ben Hinkle last year 
> about extending the "in" operator to support static/dynamic arrays.
> 
> http://www.digitalmars.com/d/archives/digitalmars/D/25164
<snip>

There are two problems with that proposal:

1. At the moment, the only use of the in operator is to determine 
whether a key is present in an AA.  Logically, therefore, for linear arrays,

     x in y

should report on whether x is an index within the bounds of y, i.e.

     x >= 0 && x < y.length

This has been talked about before:

http://www.digitalmars.com/drn-bin/wwwnews?digitalmars.D/6082


2. The result of the in operator is designed to be directly usable as a 
boolean value and to do what it says on the tin when used as such. 
Making it return an index, instead of a pointer as in for AAs does, 
screws this up totally.  As such, under Ben's proposal

     if (x in y)

would be equivalent to

     if (y.length != 0 && y[0] != x)

which is well and truly counter-intuitive.

Stewart.

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