[Haskell-cafe] Happy GLR parser creation problem

João Paulo jpaulo at di.uminho.pt
Wed Jun 2 11:56:23 EDT 2010

Hi Paul,

During my internship I developed a GLR parser generator and a grammar  
interpreter fully in Haskell, in a tool called HaGLR;

You'll find documentation on the tool at:


The tool is available as part of the UMinho Haskell libraries at:


I have to say that the tool was maintained until 2005/2006, but that,  
unfortunately, not any more;

Anyway, the tool itself consisted of very simple Haskell code, so it  
should easily be updated/altered;

Hope it helps!


João Paulo Fernandes
Universidade do Minho

Em 2010/06/02, às 11:55, Paul Jensen escreveu:

> [Apologies if this is the wrong place to ask -- there appears to be no
> Happy-specific list.]
> I'm interested in experimenting with using a GLR parser to parse some
> data that could be interpreted in different ways. I'm trying to use
> Happy's GLR mode but I am encountering an error building one of the
> examples (specifically
> http://darcs.haskell.org/happy/examples/glr/expr-eval/Expr.y):
> [Mac OS X 10.6.3]
> rhoda:expr-eval psj$ ghc --version
> The Glorious Glasgow Haskell Compilation System, version 6.12.1
> rhoda:expr-eval psj$ happy --version
> Happy Version 1.18.4 Copyright (c) 1993-1996 Andy Gill, Simon Marlow
> (c) 1997-2005 Simon Marlow
> rhoda:expr-eval psj$ happy --glr --ghc Expr.y
> shift/reduce conflicts:  9
> happy: src/ProduceGLRCode.lhs:190:11-76: Irrefutable pattern failed
> for pattern (pre, drop_me : post)
> It's the same error someone else encountered last year, described at
> http://www.haskell.org/pipermail/haskell-cafe/2009-July/063770.html .
> Does anyone have any insights into this? If Happy's GLR support isn't
> working just now, are there any other parser generators that produce
> GLR parsers that anyone would recommend having a look at?
> Many thanks,
> psj
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe

More information about the Haskell-Cafe mailing list