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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada case-statement
Date: Thu, 15 Mar 2018 17:24:05 -0500
Organization: JSA Research & Innovation
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Xref: reader02.eternal-september.org comp.lang.ada:51013
Date: 2018-03-15T17:24:05-05:00
List-Id: <comp.lang.ada>

"Stephen Davies" <joviangm@gmail.com> wrote in message 
news:c398c38e-6567-40e1-b686-7aef94e36fe3@googlegroups.com...
> On Wednesday, 14 March 2018 23:16:29 UTC, Randy Brukardt  wrote:
>
>> declare
>>   Selector : Day_Type renames Calculate_Day;
>>   subtype Weekend_Subtype is Day_Type range Sat .. Sun;
>>      -- Or use a static predicate if the range is discontiguous.
>> begin
>>   case Selector is
>>       when Mon .. Fri =>
>>          ...
>>       when  Sat | Sun =>
>>          ...
>>          case Weekend_Subtype'(Selector) is -- A type conversion works, 
>> too.
>>             when Sat =>
>>                ...
>>             when Sun =>
>>                ...
>>          end case;
>>    end case;
>> end;
>
> Unless this has changed in more recent compilers, the static predicate
> when Sat & Sun are not contiguous does not work. Gnatpro 7.0.2 complains
> about missing values. Also, attempting to use "when Weekend_Subtype" in
> the outer case-statement results in complaints about duplicate values.

It should have changed, there are a number of ACATS tests checking precisely 
this sort of thing. So far as I know, GNAT passes those tests. (And GNATPro 
7.0.2 is a looonnnng time ago, based on the ACATS tests I wouldn't expect 
much of any Ada 2012 features to work in that. I'd guess this would work in 
all of the ones I've used recently: 7.4.1, 17.1, and 18.1.)

                                                   Randy.