*RE> let justRE1 = readRegularExpression "ab |c d *"
*RE> justRE1
Just (Choice (Concat (Char 'a') (Char 'b')) (Concat (Char 'c') (Star (Char 'd'))))
*RE> let rec1 = recognize re1 where Just re1 = justRE1
*RE> rec1 "ab"
True
*RE> rec1 "cddd"
True
*RE> rec1 "c"
True
*RE> rec1 "abcd"
False
*RE> let justRE2 = readRegularExpression "(ab|a)(c|bd)"
*RE> let rec2 = recognize re2 where Just re2 = justRE2
*RE> rec2

<interactive>:1:0:
    No instance for (Show (String -> Bool))
      arising from a use of `print' at <interactive>:1:0-3
    Possible fix:
      add an instance declaration for (Show (String -> Bool))
    In a stmt of a 'do' expression: print it
*RE> justRE2
Just (Concat (Choice (Concat (Char 'a') (Char 'b')) (Char 'a')) (Choice (Char 'c') (Concat (Char 'b') (Char 'd'))))
*RE> rec2 "abd"
True
*RE> rec2 "abbd"
True
*RE> rec2 "abbbd"
False
*RE> let justRE3 = readRegularExpression "(ab|a)(c|bd|d)"
*RE> justRE3
Just (Concat (Choice (Concat (Char 'a') (Char 'b')) (Char 'a')) (Choice (Char 'c') (Choice (Concat (Char 'b') (Char 'd')) (Char 'd'))))
*RE> let rec3 = recognize re3 where Just re3 = justRE3
*RE> rec3 "abd"
True
*RE> rec3 "ad"
True
*RE> rec3 "abbd"
True
*RE> rec3 "abbbd"
False
*RE> let parserRE3 = generateParser re3 where Just re3 = justRE3
*RE> :t parserRE3
parserRE3 :: Parser ()
*RE> parse parserRE3 "abbd"
[((),"")]
*RE> parse parserRE3 "abd"
[((),""),((),"")]
*RE> parse parserRE3 "abd("
[((),"("),((),"(")]
*RE>