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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: 'raise' in aspects?
Date: Thu, 23 Oct 2014 17:42:08 -0500
Organization: Jacob Sparre Andersen Research & Innovation
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References: <85siilc88t.fsf@stephe-leake.org>
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Xref: news.eternal-september.org comp.lang.ada:22691
Date: 2014-10-23T17:42:08-05:00
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"Stephen Leake" <stephen_leake@stephe-leake.org> wrote in message 
news:85h9ywasfq.fsf@stephe-leake.org...
> Stephen Leake <stephen_leake@stephe-leake.org> writes:
>
>> The Ada mode 5.0 parser rejects this code:
>>
>>    subtype Integer_String is String
>>      with Dynamic_Predicate => Integer'Value (Integer_String) in Integer
>>             or else raise Constraint_Error with "not an integer string";
>>
>> It complains that 'raise' is not allowed here.
>>
>> ALRM Annex P says the syntax for an aspect is:
>>
>>      aspect_specification ::=
>>         with aspect_mark [=> aspect_definition] {,
>>                 aspect_mark [=> aspect_definition] }
>>
>>      aspect_mark ::= aspect_identifier['Class]
>>
>>      aspect_definition ::= name | expression | identifier
>>
>>
>> And you can't put 'raise' in an expression, which is why the Ada mode
>> parser rejects it.
>>
>> But GNAT GPL 2014 accepts it.
>>
>> Can anyone point me to RM language that allows 'raise' in aspects?
>
> For the record:
>
> ai12-0022 adds "raise_expression" to the "relation" syntax. It's a
> binding interpretation on Ada 2012
>
> http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ai12s/ai12-0022-1.txt?rev=1.13

Right, "raise_expression" can be used in any expression, not just aspects. 
Indeed, we immediately noticed that it fixed one long-standing problem in 
Ada (the need to have a return statement in every function). You can write
    raise Program_Error with "Not yet implemented";
in any function (since a raise expression matches any type), and you don't 
have to dream up a useless dummy return value to do so.

                                     Randy.