This is a first pass at an n3 [1] parser using lex/yacc.  I've used
some C++ features, although it would be pretty easy to make it
straight C, I think.  The hardest parts would be keeping track of who
needs to free char* strings, I think.  Also, it would simplify things
to make it just write the output, instead of indirecting the writes
through StreamOfTriples.

No known system dependencies beyond some lex, yacc, and C++ with STL,
but there probably are some.   As of this writing, this consitutes
about 2 days work, including borrowing and modifying an old lex/yacc
code base, and refreshing my memory on STL.  I worked without the n3
BNF until some checking at the end.

Issues:

   - what approach should we use for encoding a context
     into a stream of triples?   We can reify each statement,
     but then what do we do with the statement identifiers?
     Put them in a list, or some RDF collection, or...?
     Current Solution: a lisp-style list
   - what vocabulary to use in various places?  (see vocab array)
   - should it be an error to redefine a @prefix in the same file?
     Current Solution: no, so you can just cat n3 files, although
     that wont work if you're using "<>"
   - should we leave <> intact, or replace it with a top-level
     context identifier?  Use the filename?  Require it from user?

To Do:
 
  [ added 2002-08-30 ]
   - add support for "this"
   - change lists to use rdfns
   - MAYBE reorg to return AST instead of construct as running
   - MAYBE redo in plain C (with AST rewrite -- no need to free things)
   - use LX vocab for variables & formulas
   - use _: for genids
   - output prolog with rules recognition???
  [ from 2001-03-28 ]
   - play with adding expressions
   - pass in top-level context identifier
   - missing >-prop-> and <-prop<- and maybe some other unused features
   - input from files named on command line (use filenames in error listing)
   - validate (no-triples-out) option

[1] http://www.w3.org/DesignIssues/Notation3.html

sandro@w3.org
$Id: README,v 1.3 2002/08/30 16:20:45 sandro Exp $