Subject:
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Re: Backwards Compatibility (Was Calling all Meta-commands)
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Newsgroups:
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lugnet.cad.dev
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Date:
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Sun, 16 Mar 2003 18:10:21 GMT
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Viewed:
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5395 times
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On Sun, Mar 16, 2003 at 05:54:10PM +0000, Kevin Clague wrote:
> I think we cannot ignore the backwards compatibility issue though.
right.
> What we want is an explicit way to differentiate comments from
> meta-commands. I think defining an explicit mechanism for comments is
> completely backward compatible, because if you do not recognize the first
> token in a type 0 record, it is a comment.
>
> By using (META) or {META}, you've caused more hassles than you've solved.
> Now we programmers have to change our programs to parse type 0 records in
> two ways: The way we have today ("0 token"), *and* the new way ("0 (META)
> token").
but you just said you're doing that anyway - "if you do not recognize
the first token in a line type 0 record, it is a comment". Is adding
'{META}' to the list of recognizable tokens an issue? Also, you don't
have to add it - if you don't, the line is ignored, just like any other
comment. Perfect!
> It makes a lot more sense to me to provide an explicit way to
> differentiate comments using some keyword (COMMENT, //, #, !, etc.) You
> document the magic comment token so that no one can ever define that as a
> meta-command, and you greatly reduce the probability that someone's first
> token in a comment line is mistaken as a meta-command.
wouldn't that break backwards compatibility with ldraw.exe? Or does it
recognize any of those as a valid, but ignorable line?
> It is very common in programming language to differentiate comments from
> language significant grammar using comment start tokens than it is to
> identify the things the computer is supposed to pay attention to (i.e. (META)).
right, but it's not unhead of to use special comments as "hints" to the
program - like "#define", etc.
> Using (META) causes more work for us programmers and really doesn't solve
> much of anything.
That might be true - I'm not one of the programmers who has to implement
these, so I don't get a say here. I do think it solves the problem of
accidental meta-commands in unintentional comments.
:)
--
Dan Boger
dan@peeron.com
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