{-# LANGUAGE BangPatterns #-}
-- ------------------------------------------------------------
{- |
Module : Text.Regex.XMLSchema.Generic
Copyright : Copyright (C) 2014- Uwe Schmidt
License : MIT
Maintainer : Uwe Schmidt <uwe@fh-wedel.de>
Stability : stable
Portability: portable
Convenient functions for W3C XML Schema Regular Expression Matcher.
For internals see 'Text.Regex.XMLSchema.Regex'
Grammar can be found under <http://www.w3.org/TR/xmlschema11-2/#regexs>
-}
-- ------------------------------------------------------------
module Text.Regex.XMLSchema.Generic.Matching
( grep
, grepExt
, grepRE
, grepREwithLineNum
, match
, matchExt
, matchSubex
, sed
, sedExt
, split
, splitExt
, splitSubex
, tokenize
, tokenizeExt
, tokenize'
, tokenizeExt'
, tokenizeSubex
, matchRE
, matchSubexRE
, sedRE
, splitRE
, splitSubexRE
, tokenizeRE
, tokenizeRE'
, tokenizeSubexRE
)
where
import Control.Arrow
import Data.Maybe
import Text.Regex.XMLSchema.Generic.Regex
import Text.Regex.XMLSchema.Generic.RegexParser
import Text.Regex.XMLSchema.Generic.StringLike
{-
import Debug.Trace (traceShow)
trc :: Show a => String -> a -> a
trc msg x = traceShow (msg, x) x
-- -}
-- ------------------------------------------------------------
-- | split a string by taking the longest prefix matching a regular expression
--
-- @Nothing@ is returned in case there is no matching prefix,
-- else the pair of prefix and rest is returned
splitRE :: StringLike s => GenRegex s -> s -> Maybe (s, s)
splitRE re input
= do
(sms, rest) <- splitWithRegex re input
return (snd . head $ sms, rest)
-- | convenient function for 'splitRE'
--
-- examples:
--
-- > split "a*b" "abc" = ("ab","c")
-- > split "a*" "bc" = ("", "bc") -- "a*" matches ""
-- > split "a+" "bc" = ("", "bc") -- "a+" does not match, no split
-- > split "[" "abc" = ("", "abc") -- "[" syntax error, no split
split :: StringLike s => s -> s -> (s, s)
split = split' parseRegex
-- | split with extended syntax
splitExt :: StringLike s => s -> s -> (s, s)
splitExt = split' parseRegexExt
split' :: StringLike s => (s -> GenRegex s) -> s -> s -> (s, s)
split' parseRe re input
= fromMaybe (emptyS, input)
. (splitRE . parseRe $ re) $ input
-- ------------------------------------------------------------
-- | split a string by removing the longest prefix matching a regular expression
-- and then return the list of subexpressions found in the matching part
--
-- @Nothing@ is returned in case of no matching prefix,
-- else the list of pairs of labels and submatches and the
-- rest is returned
splitSubexRE :: StringLike s => GenRegex s -> s -> Maybe ([(s, s)], s)
splitSubexRE re input
= do
(sms, rest) <- splitWithRegex re input
return (map (first fromJust) . drop 1 $ sms, rest)
-- | convenient function for 'splitSubex', uses extended syntax
--
-- examples:
--
-- > splitSubex "({1}a*)b" "abc" = ([("1","a")],"c")
-- > splitSubex "({2}a*)" "bc" = ([("2","")], "bc")
-- > splitSubex "({1}a|b)+" "abc" = ([("1","a"),("1","b")],"c") -- subex 1 matches 2 times
-- >
-- > splitSubex ".*({x}a*)" "aa" = ([("x",""),("x","a"),("x","aa")],"")
-- > -- nondeterminism: 3 matches for a*
-- >
-- > splitSubex "({1}do)|({2}[a-z]+)" "do you know"
-- > = ([("1","do"),("2","do")]," you know")
-- > -- nondeterminism: 2 matches for do
-- >
-- > splitSubex "({1}do){|}({2}[a-z]+)" "do you know"
-- > = ([("1","do")]," you know")
-- > -- no nondeterminism with {|}: 1. match for do
-- >
-- > splitSubex "({1}a+)" "bcd" = ([], "bcd") -- no match
-- > splitSubex "[" "abc" = ([], "abc") -- syntax error
splitSubex :: StringLike s => s -> s -> ([(s, s)], s)
splitSubex re inp
= fromMaybe ([], inp) . (splitSubexRE . parseRegexExt $ re) $ inp
-- ------------------------------------------------------------
-- | The function, that does the real work for 'tokenize'
tokenizeRE :: StringLike s => GenRegex s -> s -> [s]
tokenizeRE re
= token''
where
fcs = firstChars re
re1 = mkDiff re mkUnit
token'' = token' re fcs
token1'' = token' re1 fcs
-- token' :: StringLike s => GenRegex s -> CharSet -> s -> [s]
token' re' fcs' inp
| nullS inp = []
| otherwise = evalRes . splitWithRegexCS re' fcs' $ inp
where
evalRes Nothing
= token'' (dropS 1 inp) -- re does not match any prefix
evalRes (Just (toks, rest))
| nullS tok = tok : token'' (dropS 1 rest) -- re is nullable and only the empty prefix matches
-- discard one char and try again
| otherwise = tok : token1'' rest -- real token found, next token must not be empty
where
tok = snd . head $ toks
-- | split a string into tokens (words) by giving a regular expression
-- which all tokens must match.
--
-- Convenient function for 'tokenizeRE'
--
-- This can be used for simple tokenizers.
-- It is recommended to use regular expressions where the empty word does not match.
-- Else there will appear a lot of probably useless empty tokens in the output.
-- All none matching chars are discarded. If the given regex contains syntax errors,
-- @Nothing@ is returned
--
-- examples:
--
-- > tokenize "a" "aabba" = ["a","a","a"]
-- > tokenize "a*" "aaaba" = ["aaa","a"]
-- > tokenize "a*" "bbb" = ["","",""]
-- > tokenize "a+" "bbb" = []
-- >
-- > tokenize "a*b" "" = []
-- > tokenize "a*b" "abc" = ["ab"]
-- > tokenize "a*b" "abaab ab" = ["ab","aab","ab"]
-- >
-- > tokenize "[a-z]{2,}|[0-9]{2,}|[0-9]+[.][0-9]+" "ab123 456.7abc"
-- > = ["ab","123","456.7","abc"]
-- >
-- > tokenize "[a-z]*|[0-9]{2,}|[0-9]+[.][0-9]+" "cab123 456.7abc"
-- > = ["cab","123","456.7","abc"]
-- >
-- > tokenize "[^ \t\n\r]*" "abc def\t\n\rxyz"
-- > = ["abc","def","xyz"]
-- >
-- > tokenize ".*" "\nabc\n123\n\nxyz\n"
-- > = ["","abc","123","","xyz"]
-- >
-- > tokenize ".*" = lines
-- >
-- > tokenize "[^ \t\n\r]*" = words
tokenize :: StringLike s => s -> s -> [s]
tokenize = tokenizeRE . parseRegex
-- | tokenize with extended syntax
tokenizeExt :: StringLike s => s -> s -> [s]
tokenizeExt = tokenizeRE . parseRegexExt
-- ------------------------------------------------------------
-- | split a string into tokens and delimierter by giving a regular expression
-- which all tokens must match
--
-- This is a generalisation of the above 'tokenizeRE' functions.
-- The none matching char sequences are marked with @Left@, the matching ones are marked with @Right@
--
-- If the regular expression contains syntax errors @Nothing@ is returned
--
-- The following Law holds:
--
-- > concat . map (either id id) . tokenizeRE' re == id
tokenizeRE' :: StringLike s => GenRegex s -> s -> [Either s s]
tokenizeRE' re inp0
= token'' (inp0, 0) inp0
where
fcs = firstChars re
re1 = mkDiff re mkUnit
token'' = token' re fcs
token1'' = token' re1 fcs
-- token' :: StringLike s => GenRegex s -> CharSet -> (s, Int) -> s -> [Either s s]
token' re' fcs' (uns, ! n) inp
| nullS inp = addUnmatched []
| otherwise = evalRes . splitWithRegexCS re' fcs' $ inp
where
addUnmatched
| n == 0 = id
| otherwise = ((Left $ takeS n uns) :)
addMatched t
= addUnmatched . ((Right t) :)
evalRes Nothing
= token'' (uns, n + 1) (dropS 1 inp) -- re does not match any prefix
evalRes (Just (toks, rest))
| nullS tok = addMatched tok -- re is nullable and only the empty prefix matches
$ token'' (rest, 1)
(dropS 1 rest) -- discard one char and try again
| otherwise = addMatched tok
$ token1'' (rest, 0) rest -- real token found, next token must not be empty
where
tok = snd . head $ toks
-- | convenient function for 'tokenizeRE''
--
-- When the regular expression parses as Zero, @[Left input]@ is returned, that means no tokens are found
tokenize' :: StringLike s => s -> s -> [Either s s]
tokenize' = tokenizeRE' . parseRegex
tokenizeExt' :: StringLike s => s -> s -> [Either s s]
tokenizeExt' = tokenizeRE' . parseRegexExt
-- ------------------------------------------------------------
-- | split a string into tokens (pair of labels and words) by giving a regular expression
-- containing labeled subexpressions.
--
-- This function should not be called with regular expressions
-- without any labeled subexpressions. This does not make sense, because the result list
-- will always be empty.
--
-- Result is the list of matching subexpressions
-- This can be used for simple tokenizers.
-- At least one char is consumed by parsing a token.
-- The pairs in the result list contain the matching substrings.
-- All none matching chars are discarded. If the given regex contains syntax errors,
-- @Nothing@ is returned
tokenizeSubexRE :: StringLike s => GenRegex s -> s -> [(s, s)]
tokenizeSubexRE re
= token''
where
fcs = firstChars re
re1 = mkDiff re mkUnit
token'' = token' re fcs
token1'' = token' re1 fcs
-- token' :: StringLike s => GenRegex s -> CharSet -> s -> [(s, s)]
token' re' fcs' inp
| nullS inp = []
| otherwise = evalRes . splitWithRegexCS re' fcs' $ inp
where
evalRes Nothing
= token'' (dropS 1 inp) -- re does not match any prefix
evalRes (Just (toks, rest))
| nullS tok = res ++ token'' (dropS 1 rest) -- re is nullable and only the empty prefix matches
| otherwise = res ++ token1'' rest -- token found, tokenize the rest
where
res = map (first fromJust) . tail $ toks
tok = snd . head $ toks
-- | convenient function for 'tokenizeSubexRE' a string
--
-- examples:
--
-- > tokenizeSubex "({name}[a-z]+)|({num}[0-9]{2,})|({real}[0-9]+[.][0-9]+)"
-- > "cab123 456.7abc"
-- > = [("name","cab")
-- > ,("num","123")
-- > ,("real","456.7")
-- > ,("name","abc")]
-- >
-- > tokenizeSubex "({real}({n}[0-9]+)([.]({f}[0-9]+))?)"
-- > "12.34" = [("real","12.34")
-- > ,("n","12")
-- > ,("f","34")]
-- >
-- > tokenizeSubex "({real}({n}[0-9]+)([.]({f}[0-9]+))?)"
-- > "12 34" = [("real","12"),("n","12")
-- > ,("real","34"),("n","34")]
-- >
-- > tokenizeSubex "({real}({n}[0-9]+)(([.]({f}[0-9]+))|({f})))"
-- > "12 34.56" = [("real","12"),("n","12"),("f","")
-- > ,("real","34.56"),("n","34"),("f","56")]
tokenizeSubex :: StringLike s => s -> s -> [(s, s)]
tokenizeSubex = tokenizeSubexRE . parseRegexExt
-- ------------------------------------------------------------
-- | sed like editing function
--
-- All matching tokens are edited by the 1. argument, the editing function,
-- all other chars remain as they are
sedRE :: StringLike s => (s -> s) -> GenRegex s -> s -> s
sedRE edit re = concatS . map (either id edit) . tokenizeRE' re
-- | convenient function for 'sedRE'
--
-- examples:
--
-- > sed (const "b") "a" "xaxax" = "xbxbx"
-- > sed (\ x -> x ++ x) "a" "xax" = "xaax"
-- > sed undefined "[" "xxx" = "xxx"
sed :: StringLike s => (s -> s) -> s -> s -> s
sed edit = sedRE edit . parseRegex
sedExt :: StringLike s => (s -> s) -> s -> s -> s
sedExt edit = sedRE edit . parseRegexExt
-- ------------------------------------------------------------
-- | match a string with a regular expression
matchRE :: StringLike s => GenRegex s -> s -> Bool
matchRE = matchWithRegex
-- | convenient function for 'matchRE'
--
-- Examples:
--
-- > match "x*" "xxx" = True
-- > match "x" "xxx" = False
-- > match "[" "xxx" = False
match :: StringLike s => s -> s -> Bool
match = matchWithRegex . parseRegex
-- | match with extended regular expressions
matchExt :: StringLike s => s -> s -> Bool
matchExt = matchWithRegex . parseRegexExt
-- ------------------------------------------------------------
-- | match a string with a regular expression
-- and extract subexpression matches
matchSubexRE :: StringLike s => GenRegex s -> s -> [(s, s)]
matchSubexRE re = map (first fromJust) . fromMaybe [] . matchWithRegex' re
-- | convenient function for 'matchRE'
--
-- Examples:
--
-- > matchSubex "({1}x*)" "xxx" = [("1","xxx")]
-- > matchSubex "({1}x*)" "y" = []
-- > matchSubex "({w}[0-9]+)x({h}[0-9]+)" "800x600" = [("w","800"),("h","600")]
-- > matchSubex "[" "xxx" = []
matchSubex :: StringLike s => s -> s -> [(s, s)]
matchSubex = matchSubexRE . parseRegexExt
-- ------------------------------------------------------------
-- | grep like filter for lists of strings
--
-- The regular expression may be prefixed with the usual context spec \"^\" for start of string,
-- and "\\<" for start of word.
-- and suffixed with \"$\" for end of text and "\\>" end of word.
-- Word chars are defined by the multi char escape sequence "\\w"
--
-- Examples
--
-- > grep "a" ["_a_", "_a", "a_", "a", "_"] => ["_a_", "_a", "a_", "a"]
-- > grep "^a" ["_a_", "_a", "a_", "a", "_"] => ["a_", "a"]
-- > grep "a$" ["_a_", "_a", "a_", "a", "_"] => ["_a", "a"]
-- > grep "^a$" ["_a_", "_a", "a_", "a", "_"] => ["a"]
-- > grep "\\<a" ["x a b", " ax ", " xa ", "xab"] => ["x a b", " ax "]
-- > grep "a\\>" ["x a b", " ax ", " xa ", "xab"] => ["x a b", " xa "]
grep :: StringLike s => s -> [s] -> [s]
grep = grep' parseRegex'
-- | grep with extended regular expressions
grepExt :: StringLike s => s -> [s] -> [s]
grepExt = grep' parseRegexExt'
grep' :: StringLike s => (String -> GenRegex s) -> s -> [s] -> [s]
grep' parseRe = grepRE . parseContextRegex parseRe
-- | grep with already prepared Regex (ususally with 'parseContextRegex')
grepRE :: StringLike s => GenRegex s-> [s] -> [s]
grepRE re = filter (matchRE re)
-- | grep with Regex and line numbers
grepREwithLineNum :: StringLike s => GenRegex s -> [s] -> [(Int, s)]
grepREwithLineNum re = filter (matchRE re . snd) . zip [(1::Int)..]
-- ------------------------------------------------------------