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From: jscheibl@mason2.gmu.edu (Jack W Scheible)
Subject: Re: Limitations of Ada
Date: 1996/08/05
Message-ID: <4u50g1$li1@portal.gmu.edu>#1/1
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references: <4tr86p$fvd@rational.rational.com> <4tsvs7$ctk@portal.gmu.edu>
 <DvJyKB.9DC@thomsoft.com>
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organization: George Mason University, Fairfax, Virginia, USA
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newsgroups: comp.lang.ada
Date: 1996-08-05T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <DvJyKB.9DC@thomsoft.com> kst@thomsoft.com (Keith Thompson) writes:
>In <4tsvs7$ctk@portal.gmu.edu> jscheibl@mason2.gmu.edu (Jack W Scheible) writes:
>> There is no reason at all that the C pre-processor cannot be
>> run on Ada source before sending it to the compiler.  Therefore,
>> one _can_ use macros, but it is neither standard nor advisable - 
>> macros can be a source of very hard-to-find bugs.
>
>Actually, there is a reason.  The C preprocessor chokes on some Ada
>constructs.  The ISO C standard requires the input to the preprocessing
>phase to be a valid token stream.  I don't remember the exact details,
>but one consequence is that an apostrophe that's not part of a character
>literal (e.g., in an Ada attribute) is illegal.
>
>Here's an example:
>
>package Foo is
>#ifdef FIRST
>   X : Integer := Integer'First;
>#else
>   X : Integer := Integer'Last;
>#endif
>end Foo;
>
>The "cc -E" command under Solaris complains:
>
>"foo.ads", line 5: invalid input token: 'Last;
>

The above code works just fine with the command "cpp -P" under Solaris.
It is _still_ a bad idea.

-jack