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GHC 9.10.3 · lts/ghc-9.10.x · 248f8f0 · 2026-10-05

Modulehxt-regex-xmlschema-9.2.0.7Haskell2010

Text.Regex.XMLSchema.Generic.Matching

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

  • 25 values
valuegrep :: StringLike s => s -> [s] -> [s]
#

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 "]
valuegrepExt :: StringLike s => s -> [s] -> [s]
#

grep with extended regular expressions

valuematch :: StringLike s => s -> s -> Bool
#

convenient function for matchRE

Examples:

match "x*" "xxx" = True
match "x" "xxx"  = False
match "[" "xxx"  = False
valuematchSubex :: StringLike s => s -> s -> [(s, s)]
#

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"                            = []
valuesed :: StringLike s => (s -> s) -> s -> s -> s
#

convenient function for sedRE

examples:

sed (const "b") "a" "xaxax"       = "xbxbx"
sed (\ x -> x ++ x) "a" "xax"     = "xaax"
sed undefined       "[" "xxx"     = "xxx"
valuesplit :: StringLike s => s -> s -> (s, s)
#

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
valuesplitSubex :: StringLike s => s -> s -> ([(s, s)], s)
#

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
valuetokenize :: StringLike s => s -> s -> [s]
#

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
valuetokenize' :: StringLike s => s -> s -> [Either s s]
#

convenient function for tokenizeRE'

When the regular expression parses as Zero, [Left input] is returned, that means no tokens are found

valuetokenizeSubex :: StringLike s => s -> s -> [(s, s)]
#

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")]
valuesedRE :: StringLike s => (s -> s) -> GenRegex s -> s -> s
#

sed like editing function

All matching tokens are edited by the 1. argument, the editing function, all other chars remain as they are

valuesplitRE :: StringLike s => GenRegex s -> s -> Maybe (s, s)
#

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

valuesplitSubexRE :: StringLike s => GenRegex s -> s -> Maybe ([(s, s)], s)
#

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

valuetokenizeRE' :: StringLike s => GenRegex s -> s -> [Either s s]
#

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
valuetokenizeSubexRE :: StringLike s => GenRegex s -> s -> [(s, s)]
#

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