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Date: Fri, 3 May 2013 18:02:10 -0700 (PDT)
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Subject: Re: Ada 2012: In-out parameters for functions
From: Adam Beneschan <adam@irvine.com>
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Date: 2013-05-03T18:02:10-07:00
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On Friday, May 3, 2013 4:29:46 PM UTC-7, Randy Brukardt wrote:

> I agree that named notation should include the direction of the parameter, 
> but again its way too late to fix. The best syntax would have been
>      Proc (In_Param => A, Out_Param <= B, In_Out_Param <=> C);
> but unfortunately "<=" is used for less-than-or-equals and trying to use it 
> in this context would be ambiguous.
> 
> So the best practical syntax would be:
>      Proc (In_Param -> A, Out_Param <- B, In_Out_Param <-> C);
> But adding new compound delimiters has never been done (lexical elements are 
> unchanged since Ada 83, the only changes being to allow Unicode characters 
> in identifiers and strings), and this scares people. Moreover, we don't have 
> any current delimiters that have three characters. So this would likely have 
> a lot of change to tools, at a very fundemental level.

This particular change would break any code that looks like

      if X<-1 then ...

and you just gotta know that there's some out there, no matter how ugly it looks. 

Ada 80 (?) would have said

    Proc (In_Param =: A, Out_Param := B, In_Out_Param :=: C)

Don't know why they didn't stick with it.

                                   -- Adam