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Newsgroups: comp.lang.ada
Subject: Re: lexical ambiguity
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From: Keith Thompson <kst-u@mib.org>
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Date: Mon, 05 Jun 2006 20:27:11 GMT
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"Frank J. Lhota" <flhota@NOSPAM.ll.mit.edu> writes:
> Jeffrey R. Carter wrote:
>> Yes, but it's good to be precise.
>
> Absolutely! I should have said "qualified expression" in my original
> post. Sorry for any confusion that I may have caused.
>
>>>     Foo'(',',',',',' ... )
>> Clearly you have an evil mind :)
>
> Well, there is a good reason to consider this worst case scenario. I
> have seen quick and dirty Ada lexers that try to determine if a single
> quote starts a character literal by looking ahead 2 character. As this
> scenario shows, this approach is not guaranteed to work.

If I recall correctly, it's sufficient to remember what the previous
token was.  A character literal cannot follow an identifier.

I think that might break down if an implementation chooses to define
an attribute with a single-character name, but I don't remember the
details; presumably no implementation will actually do this.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center             <*>  <http://users.sdsc.edu/~kst>
We must do something.  This is something.  Therefore, we must do this.