Re: Gnat GPL 2010 available soon (conditional expressions)

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Mon, 5 Jul 2010 15:47:41 -0700 (PDT), Phil Clayton wrote:

> On Jul 5, 2:12�pm, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
> wrote:
>> On Sun, 4 Jul 2010 18:27:04 -0700 (PDT), Phil Clayton wrote:
>>> In my view, condition expressions are a step in the right direction...
>>> but I'm the sort of person who wants to write an array aggregate like
>>
>>> � (for I in 1 .. 5 => (for J in 1 .. 7 => (if I = J then 1.0 else
>>> 0.0)))
>>
>> � (for I in 1..5 => (for J in 1..7 => Float (Boolean'Pos (I = J))))
> 
> Yep, I should have seen that one coming straight back... and taken
> steps to avoid it :)

BTW, is your construct 1) a macro expansion (as I remember PL/1
preprocessor also had %for statement alike) and how far are you ready to go
allowing "for" macros? Loops unrolling? Or else 2) it is an attempt to name
the components of an array element index. In the latter case

   (I, J : others => <an expression involving I,J>)
   (I : 1..5 => <an expression involving I>)
   (Odd : 1 | 3 | 5 | 7 => <an expression involving Odd>, others => 0.0)
   etc

looks to me more consistent with existing Ada, e.g. when Error : others =>
in exception handlers.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de