Re: very specific question on Ada syntax

[Tucker Taft <stt@averstar.com>]

Mario Amado Alves wrote:
> 
> >    len := Color'image(Color'first)'length;
> 
> Yes, of course. Thanks. Just found an example in the RM itself:
> 
>   Rainbow'Base'First           4.1.4(16)
> 
> This was because I was wondering if a character literal could be tokenized
> without context. I guess not. In
> 
>   A'B'C
> 
> 'B' has the form of a character literal, but it is not it. I could perhaps
> rely on the fact (?) that there is no attribute of only one letter, but
> that is twisted to say the least.

Anyone who has built a production-quality Ada compiler will
know that distinguishing the attribute "'" from the character literal "'"..."'"
requires some special finagling.  The technique most of us have
adopted is to keep track of whether the immediately prior token
can be the last token of a "name", and if so, interpret
the "'" as an attribute "tic" rather than as a character-literal "quote".
In particular, if the prior token is:
    identifier
    )
    string-literal
    ALL
    character-literal

then a "'" should be interpreted as an attribute "tic"; otherwise
presume it is the beginning of a character literal.

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-- 
-Tucker Taft   stt@avercom.net   http://www.averstar.com/~stt/
Chief Technology Officer, AverCom, Inc. (A Titan Company) Burlington, MA  USA
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