[mercury-users] moose and epsilon reductions

Fergus Henderson fjh at cs.mu.OZ.AU
Tue Dec 9 03:12:46 AEDT 2003

On 03-Dec-2003, obo at ruk.cuni.cz <obo at ruk.cuni.cz> wrote:
> (I know that currently there is hardly any support for the moose... But
> however.)
> How do I implement epsilon reductions in moose?
> Am I expecting too much from an LALR parser, or is moose weaker than LALR,
> or is this just a bug in the algorithm of removing epsilon reductions?

The problem that you describe looks like a bug in Moose.
I had a quick look at the Moose sources, and it is clear that
Moose is supposed to be able to handle epsilon productions.
The immediate cause of the error is a map.lookup failure when computing
the action table.  But it wasn't obvious as to exactly what the ultimate
cause of the bug was or how to fix it.

I have added a mention of this bug to the moose/README and moose/BUGS files.

Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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