DMD 0.177 release [Length in slice expressions]

[Pragma]

Andrei Alexandrescu (See Website For Email) wrote:
> 
> A simpler grammar would have been to simply allow:
> 
> UnaryExpression:
>     PostfixExpression
>     & UnaryExpression
>     ... etc. etc. ...
>     $ PostfixExpression
> 
> But this would have been ambiguous. If the compiler sees "$-1", then the 
> bad grammar says that's a unary use of $ because -1 is a 
> PostfixExpression. But that's not what we wanted! We wanted $ to be 
> nullary. That's why I needed to put all the cases in UnaryExpression.
> 

Nice post, and one heck of an argument!

FWIW, I advocated something similar during the last round of debates 
before the '$' operator was introduced.  What I wanted to see was '$' to 
become like 'this' within slice and array expressions, so that the 
issues regarding 'length' could be resolved.  In essence one could 
simply say '$.length' and mean 'the length of the current array':

b[0 .. $.length];
a[0 .. $.getIndexOf(';')];

So in essence, every use of '$' would be a 'nullary' operator - an alias 
if you will.

I'd imagine that extending things in this manner would simplify things 
grammatically while allowing for a wider category of uses.  However, it 
doesn't solve the issue that you brought up, and that I've quoted above.

c[$-1];

It looks like it should be an implicit cast of the '$' to a size_t 
(length), via it's use in an expression.  Any thoughts on this?

-- 
- EricAnderton at yahoo