From: Markus <markus@...>
Date: 2004-10-11T23:45:55+09:00
Subject: Re: ANN: Free-form-operators patch

> "Yukihiro Matsumoto" <matz@ruby-lang.org> schrieb im Newsbeitrag
> > * I am against for user defined operator precedence.  It's just
> >   wrong.  So forget about that idea.  All user defined operators
> >   should have same precedence, even if they are allowed.
> 
> On Mon, 2004-10-11 at 02:19, Robert Klemme wrote:
> +2 (Also, since precedence is typically implemented in the parser I can
> imagine that user defined precedence makes for awful changes in the parser
> which has considerable complexity already AFAIK.)

     The parser part (at least in isolation) isn't too bad.  Instead of
one operator token (tGENERIC_OP) you have a set of them (tOP1..tOP9 say)
which have a range of precedences by varying semantics.  The user then
gets to choose which token to use for each op.  Since these could also
be used for many/most of the built-in operators, it might actually
simplify the parser.

     The complication come when you start to work out the "scope" of a
declared operator precedence; if it is very global the chance of
conflict (I want it to be 7 in my library, you want it to be 3 in yours,
and poor Joe requires both libraries) goes way up.  But if it is not as
global as global can be, there are other problems.  The best I have been
able to do is come up with a compromise that clearly has both problems.

-- Markus