Re: Luma errors

[Roberto Ierusalimschy <roberto@...>]

> [...]
> 
> And, so, the <> became superfluous. So, maybe the % is superfluous too.
> (But maybe I do not recall correctly...)

The '%' is not gratuitous. The patch for Luma gives definitions
priority over non terminals. This seems to me a big mistake; local names
should always have priority over further ones.

If I write something like

  p = re.compile([[p -> . p / '']], defs)

I will have weird surprises if 'p' happens to be defined in 'defs'.

We could ameliorate the problem by raising an error if a non-terminal
is defined with the name of a definition, but this still seems wrong
to me. A correct, stand-alone grammar could be made invalid depending
of the definitions given in its compilation.

(The patch also distinguishes between pre-definitions [that still need
the '%'] and 'non-pre'definitions; this distinction also creates some
confusion).

In my view, the correct think would be to give non-terminals priority
over definitions; this is harder to implement, but not impossible.

-- Roberto