Copyright (C) 2009 The University of Melbourne

Doesn't handle epsilon productions properly -- throws an exception
when computing the action table:

	Uncaught Mercury exception:
	Software Error: map__lookup: key not found
		Key Type: grammar.symbol
		Key Functor: terminal/1
		Value Type: list.list(lalr.item)
	Stack dump follows:
	   0       pred exception.throw/1-0 (erroneous) (exception.m:304)
	   1       pred require.error/1-0 (erroneous) (require.m:101)
	   2       pred require.report_lookup_error/3-0 (erroneous) (require.m:89)
	   3       pred map.lookup/3-0 (det) (map.m:469)
	   4       pred tables.IntroducedFrom__pred__actions2__119__6/8-0 (det) (tables.m:121)
	   5    2* pred list.foldl2/6-0 (det) (list.m:1356 and others)
	   7       pred tables.actions2/12-0 (det) (tables.m:119)
	   8       pred tables.actions1/10-0 (det) (tables.m:91)
	   9       pred tables.actions/8-0 (det) (tables.m:72)
	  10       pred moose.process_2/8-0 (det) (moose.m:200)
	  11       pred moose.process/3-0 (det) (moose.m:133)
	  12       pred moose.main2/4-0 (det) (moose.m:59)
	  13       pred moose.main/2-0 (det) (moose.m:36)

Doesn't give good error messages if :- action is used but the rule
doesn't exist. 

Doesn't give good error messages for misplaced semicolons.

	:- rule init_declarator(init_declarator).
	init_declarator(init_declarator(D, Init)) --->
        	  declarator(D) ; { Init = no }.

If there is some error in the grammar moose will write an empty or broken .m
file.  This may be a problem in some cases.