Text.ParserCombinators.UU.Demo.MergeAndPermute

Documentation

type Grammar a = Gram (P (Str Char String LineColPos)) a

show_demos :: IO ()

By running the function show_demos you will get a demonstration of the merging parsers.

>>> run ((,,) <$> two pA <||> three pB <||> pBetween 2 4 pC )  "cababbcccc"
 Result: ("aa",("b","b","b"),["c","c","c","c"])
 Correcting steps: 
   The token 'c' was not consumed by the parsing process.

>>> run (amb (mkParserM ((,) <$> pmMany ((,) <$>  pA <*> pC) <||> pmMany pB)))    "aabbcaabbccc"
 Result: [([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),
          ([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),
          ([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),
          ([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),
          ([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),
          ([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"]),([("a","c"),("a","c"),("a","c"),("a","c")],["b","b","b","b"])]

>>> run (pmMany(pABC))                                                            "a2a1b1b2c2a3b3c1c3"
 Result: ["2a","1a","3a"]

>>> run ((,)    <$> pBetween 2 3 pA <||> pBetween 1 2 pB)                         "abba"
 Result: (["a","a"],["b","b"])

>>> run ((,)    <$> pBetween 2 3 pA <||> pBetween 1 2 pB)                         "bba"
 Result: (["a","a"],["b","b"])
 Correcting steps: 
   Inserted  'a' at position LineColPos 0 3 3 expecting 'a'

>>> run (amb (mkParserM( ((,)    <$> pBetween 2 3 pA <||> pBetween 1 2 pA))))      "aaa"
 Result: [(["a","a"],["a"]),(["a","a"],["a"]),(["a","a"],["a"])]

The a at the right hand side can b any of the three a-s in the input:

>>> run ((,)    <$> pAtLeast 3 pA <||> pAtMost 3 pB)                              "aabbbb"
 Result: (["a","a","a"],["b","b","b"])
 Correcting steps: 
   Deleted   'b' at position LineColPos 0 5 5 expecting 'a'
   Inserted  'a' at position LineColPos 0 6 6 expecting 'a'

>>> run ((,)    <$> pSome pA <||> pMany pB)                                       "abba"
 Result: (["a","a"],["b","b"])

>>> run ((,)    <$> pSome pA <||> pMany pB)                                       "abba"
 Result: (["a","a"],["b","b"])

>>> run ((,)    <$> pSome pA <||> pMany pB)                                       ""
 Result: (["a"],[])
 Correcting steps: 
   Inserted  'a' at position LineColPos 0 0 0 expecting one of ['a', 'b']

>>> run ((,)    <$> pMany pB <||> pSome pC)                                       "bcbc"
 Result: (["b","b"],["c","c"])

>>> run ((,)    <$> pSome pB <||> pMany pC)                                       "bcbc"
 Result: (["b","b"],["c","c"])

>>> run ((,,,)   <$> pSome pA <||> pMany pB <||> pC <||> (pNat `opt` 5) )         "bcab45"
 Result: (["a"],["b","b"],"c",45)

>>> run ((,)    <$> pMany (pA <|> pB) <||> pSome  pNat)                           "1ab12aab14"
 Result: (["a","b","a","a","b"],[1,12,14])

>>> run ( (,)   <$> ((++) <$> pMany pA <||> pMany pB) <||> pC)                    "abcaaab"
 Result: (["a","a","a","a","b","b"],"c")

>>> run (pc `mkParserS` ((,) <$> pMany pA <||> pMany pB))                         "acbcacb"
 Result: (["a","a"],["b","b"])

pA, pC, pB :: Grammar String

pNat :: Grammar Int

two :: Applicative f => f [a] -> f [a]

two recognises two instance of p as part of the input sequence

three :: Applicative f => f a -> f (a, a, a)

three recognises two instance of p as part of the input sequence and concatenates the results

pABC :: Grammar Char

pABC minimcs a series of events (here an a, a b and a c), which belong to the same transaction. The transaction is identified by a digit: hence a full transaction is a string like "a5b5c5". The third element in the body of show_demos below shows how the different transactions can be recovered from a log-file which contains all events generated by a collection of concurrently running transactions.