Algorithm7_1_1C_Sub.hs

import Parser
import BNF2Props
import System.IO
import System.Environment
import Data.Maybe
import Data.List

main =
  putStr "Input a grammar file: " >>       -- grammar.txt
  getLine >>= \filename ->
  openFile filename ReadMode >>= \handle ->
  hGetContents handle >>= \file -> 
  let bnf = (fst . fromJust . parse syntax') file ; cs = (fst . fromJust . parse chars) file in
  -- mapM_ print bnf >>
  -- mapM_ print cs >>
  mapM_ print (nub $ concatMap (\rule -> rule2clauses' rule cs) bnf) >>
  -- print (length $ nub $ concatMap (\rule -> rule2clauses' rule cs) bnf) >>
  hClose handle

rule2clauses' :: (String,[String]) -> [Char] -> [Clause]
rule2clauses' (_,[])     _  = []
rule2clauses' (s,[t])    cs = rule2clauses s t cs
rule2clauses' (s,(t:ts)) cs = rule2clauses s t cs ++ rule2clauses' (s,ts) cs

{- grammar.txt

<expression> ::= <term> | <expression> '+' <term> | <expression> '-' <term>
<term> ::= <factor> | '-' <factor> | <term> '*' <factor> | <term> '/' <factor>
<factor> ::= <variable> | <constant> | '(' <expression> ')'
<variable> ::= <letter> | <variable> <letter> | <variable> <digit>
<letter> ::= 'a' | 'b' | 'c'
<constant> ::= <digit> | <constant> <digit>
<digit> ::= '0' | '1'

-}