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Re: [PATCH] Do not allow identifiers that start with a negative number.


From: Hans Aberg
Subject: Re: [PATCH] Do not allow identifiers that start with a negative number.
Date: Sat, 8 Jan 2011 23:54:33 +0100

On 8 Jan 2011, at 22:37, Paul Eggert wrote:

Yes, Bison experts can parse the code because they know all
the ins and outs of the rules.  But surely ordinary users will
be confused.  For example, if "--x" is an identifier, then
in C code

  $--x

is supposed to be parsed as "$" applied to the identifier "--x", but

  *--x

is supposed to be parsed as "*" applied to "--" applied to
the identifier "x".

This is the sort of confusion I am worried about.

In a parser I am writing on top of guile, I have very restricted identifiers, but in order to allow any passed down to guile, one can use quotes '...'. This avoids any confusion. In infix notation, x-y could be interpreted as the expression x - y, but 'x-y' is easy to see as an identifier.

I gather you are discussing putting labels on the rule items. Is that available in the current distribution?




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