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ANNOUNCE: Frown - an LALR(k) Parser Generator for Haskell (version 0.6, beta)
-----------------------------------------------------------------------------
I'm pleased to announce the first release of Frown (version 0.6,
andromeda release), an LALR(k) Parser Generator for Haskell 98.
This is a beta quality release.
Frown's salient features are:
o The generated parsers are time and space efficient. On the downside,
the parsers are quite large.
o Frown generates four different types of parsers. As a common
characteristic, the parsers are genuinely functional (ie `table-free');
the states of the underlying LR automaton are encoded as mutually
recursive functions. Three output formats use a typed stack
representation, one format due to Ross Paterson (code=stackless)
works even without a stack.
o Encoding states as functions means that each state can be treated
individually as opposed to a table driven-approach, which
necessitates a uniform treatment of states. For instance,
look-ahead is only used when necessary to resolve conflicts.
o Frown comes with debugging and tracing facilities; the standard
output format due to Doaitse Swierstra (code=standard) may be
useful for teaching LR parsing.
o Common grammatical patterns such as repetition of symbols can be
captured using rule schemata. There are several predefined rule
schemata.
o Terminal symbols are arbitrary variable-free Haskell patterns or
guards. Both terminal and nonterminal symbols may have an arbitrary
number of synthesized attributes.
o Frown comes with extensive documentation; several example grammars
are included.
Furthermore, Frown supports the use of monadic lexers, monadic
semantic actions, precedences and associativity, the generation of
backtracking parsers, multiple start symbols, error reporting and a
weak form of error correction.
Frown is available in source form, which can be compiled with GHC
version 5.02+. The source code and further information is available
on the Frown home page
http://www.informatik.uni-bonn.de/~ralf/frown/index.html
Please send any bug reports and comments to ralf@informatik.uni-bonn.de.
Happy frowning, Ralf
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