Paket: frown (0.6.2.3-4)

LALR(k) parser generator

Frown is an LALR(k) parser generator for Haskell 98 written in Haskell 98.

Its salient features are:

   -  The generated parsers are time and space efficient. On the downside, the
      parsers are quite large.
   -  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, and one format due to Ross Paterson (code=stackless)
      works even without a stack.
   -  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.
   -  Frown comes with debugging and tracing facilities; the standard output
      format due to Doaitse Swierstra (code=standard) may be useful for
      teaching LR parsing.
   -  Common grammatical patterns such as repetition of symbols can be
      captured using rule schemata. There are several predefined rule
      schemata.
   -  Terminal symbols are arbitrary variable-free Haskell patterns or guards.
      Both terminal and nonterminal symbols may have an arbitrary number of
      synthesized attributes.
   -  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.