Question on use of ! instead of |

Question on use of ! instead of |

[James Alan Farrell]

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Hi all,
I'm working on a program to analyze Ada code using ASIS.  We use ACATS 
to test our software, and this has turned up some behavior I'm having 
troubles explaining.

ACATS test a2a031a.adb (below) has a line in it:

      VAR := (A!B => E2, C ! D => 0);    -- AGGREGATE.

According to ASIS, "A!B" is an identifier.  If I put spaces around the ! 
then A and B are identifiers and things work the way I expect, and if I 
replace the ! with a | again things work the way I expect.

Could this be a bug in the compiler or in ASIS?

I couldn't find ! in the ARM.  It's supposed to be a direct replacement 
for |, correct?  (ie, they should work the same semantically and 
syntactically?)

I am using gnat 3.15p and the appropriate matching version of ASIS.

Thanks,
James Alan Farrell
Grammatech, inc.


-- A2A031A.ADA

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--*
-- CHECK THAT AN EXCLAMATION MARK CAN REPLACE A VERTICAL BAR WHEN THE
-- VERTICAL BAR IS USED AS A SEPARATOR.

-- CONTEXTS ARE:
--   AS A CHOICE IN A VARIANT PART
--   IN A DISCRIMINANT CONSTRAINT
--   IN A CASE STATEMENT CHOICE
--   IN AN AGGREGATE
--   IN AN EXCEPTION HANDLER.

-- JBG 5/25/85

WITH REPORT; USE REPORT;
PROCEDURE A2A031A IS

      TYPE ENUM IS (E1, E2, E3);
      TYPE REC (A, B : ENUM) IS
           RECORD
                C : INTEGER;
                CASE A IS
                     WHEN E1 ! E2 =>     -- CHOICE OF VARIANT.
                          D : INTEGER;
                     WHEN E3 =>
                          E : FLOAT;
                END CASE;
           END RECORD;

      EX1, EX2, EX3 : EXCEPTION;

      VAR  : REC (A!B => E2);            -- DISCRIMINANT CONSTRAINT.

      EVAR : ENUM := E2;

BEGIN

      TEST ("A2A031A", "CHECK USE OF ! AS SEPARATOR IN PLACE OF |");

      CASE EVAR IS
           WHEN E3 => NULL;
           WHEN E2!E1 => NULL;           -- CASE STATEMENT CHOICE.
      END CASE;

      VAR := (A!B => E2, C ! D => 0);    -- AGGREGATE.

      RESULT;
EXCEPTION
      WHEN EX1!EX2 ! EX3 => NULL;        -- EXCEPTION HANDLER.
END A2A031A;

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begin:vcard
fn:James Alan Farrell
n:Farrell;James
org:GrammaTech
version:2.1
end:vcard

Re: Question on use of ! instead of |

[Manuel G. R.]

James Alan Farrell wrote:
> According to ASIS, "A!B" is an identifier.  If I put spaces around the ! 
> then A and B are identifiers and things work the way I expect, and if I 
> replace the ! with a | again things work the way I expect.
> 
> Could this be a bug in the compiler or in ASIS?

In ASIS for GNAT, I think.

> 
> I couldn't find ! in the ARM.  It's supposed to be a direct replacement 
> for |, correct?  (ie, they should work the same semantically and 
> syntactically?)
> 

Yes, they should. This is one of the obsolescent features in Ada 95: "A 
vertical line character (|) can be replaced by an exclamation mark (!) 
where used as a delimiter."

http://www.adaic.com/standards/95lrm/html/RM-J-2.html


-- 
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Tutorial de programaci�n en Ada: 
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Re: Question on use of ! instead of |

[Steve]

"James Alan Farrell" <jfarrell@nospam.com> wrote in message 
news:42b96967$1_1@newsfeed.slurp.net...
> Hi all,
> I'm working on a program to analyze Ada code using ASIS.  We use ACATS
> to test our software, and this has turned up some behavior I'm having
> troubles explaining.
>
> ACATS test a2a031a.adb (below) has a line in it:
>
>      VAR := (A!B => E2, C ! D => 0);    -- AGGREGATE.
>
> According to ASIS, "A!B" is an identifier.  If I put spaces around the !
> then A and B are identifiers and things work the way I expect, and if I
> replace the ! with a | again things work the way I expect.
>

Ada 95 Reference Manual
2.3 Identifiers

  identifier ::= identifier_letter{[underline]letter_or_digit}

I would certainly say that A!B is not an identifier.

Seems worthy of sending a report to AdaCore.

report@gnat.com

(as I recall)

Steve
(The Duck)

Re: Question on use of ! instead of |

[James Alan Farrell]

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Manuel G. R. wrote:
> James Alan Farrell wrote:
> 
>> According to ASIS, "A!B" is an identifier.  If I put spaces around the 
>> ! then A and B are identifiers and things work the way I expect, and 
>> if I replace the ! with a | again things work the way I expect.
>>
>> Could this be a bug in the compiler or in ASIS?
> 
> 
> In ASIS for GNAT, I think.
> 

I was thinking about this last night.  Seems the parser needs to 
determine where the identifier begins and ends (the lexer actually), so 
that needs to be saying the three characters are the identifier.  The 
bug has to be here (well before ASIS gets involved).

But if that were the case, it should fail with an error that A!B is 
undefined.  So it appears that there is a second place place where the 
delimiter is looked for - when the declaration of A is looked up.

Now there's a subtlety with this test case:  A and B are parameters to a 
variant record.  But nothing in the record depends on B.  So if B is not 
set, executable code would be produced that still produces the expected 
output, and the ACATS test could still pass.

>>
>> I couldn't find ! in the ARM.  It's supposed to be a direct 
>> replacement for |, correct?  (ie, they should work the same 
>> semantically and syntactically?)
>>
> 
> Yes, they should. This is one of the obsolescent features in Ada 95: "A 
> vertical line character (|) can be replaced by an exclamation mark (!) 
> where used as a delimiter."
> 
> http://www.adaic.com/standards/95lrm/html/RM-J-2.html
> 
> 


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begin:vcard
fn:James Alan Farrell
n:Farrell;James
org:GrammaTech
version:2.1
end:vcard