Hledger.Utils.Regex

Easy regular expression helpers, currently based on regex-tdfa. These should:

• be cross-platform, not requiring C libraries
• support unicode
• support extended regular expressions
• support replacement, with backreferences etc.
• support splitting
• have mnemonic names
• have simple monomorphic types
• work with simple strings

Regex strings are automatically compiled into regular expressions the first time they are seen, and these are cached. If you use a huge number of unique regular expressions this might lead to increased memory usage. Several functions have memoised variants (*Memo), which also trade space for time.

Currently two APIs are provided:

• The old partial one (with ' suffixes') which will call error on any problem (eg with malformed regexps). This comes from hledger's origin as a command-line tool.
• The new total one which will return an error message. This is better for long-running apps like hledger-web.

Current limitations:

• (?i) and similar are not supported

Regexp type and constructors

data Regexp

Regular expression. Extended regular expression-ish syntax ? But does not support eg (?i) syntax.

Instances

Eq Regexp

Defined in Hledger.Utils.Regex

Methods

(==) :: Regexp -> Regexp -> Bool

(/=) :: Regexp -> Regexp -> Bool

Ord Regexp

Defined in Hledger.Utils.Regex

Methods

compare :: Regexp -> Regexp -> Ordering

(<) :: Regexp -> Regexp -> Bool

(<=) :: Regexp -> Regexp -> Bool

(>) :: Regexp -> Regexp -> Bool

(>=) :: Regexp -> Regexp -> Bool

max :: Regexp -> Regexp -> Regexp

min :: Regexp -> Regexp -> Regexp

Read Regexp

Defined in Hledger.Utils.Regex

Methods

readsPrec :: Int -> ReadS Regexp

readList :: ReadS [Regexp]

readPrec :: ReadPrec Regexp

readListPrec :: ReadPrec [Regexp]

Show Regexp

Defined in Hledger.Utils.Regex

Methods

showsPrec :: Int -> Regexp -> ShowS

show :: Regexp -> String

showList :: [Regexp] -> ShowS

ToJSON Regexp

Defined in Hledger.Utils.Regex

Methods

toJSON :: Regexp -> Value

toEncoding :: Regexp -> Encoding

toJSONList :: [Regexp] -> Value

toEncodingList :: [Regexp] -> Encoding

RegexLike Regexp String

Defined in Hledger.Utils.Regex

Methods

matchOnce :: Regexp -> String -> Maybe MatchArray

matchAll :: Regexp -> String -> [MatchArray]

matchCount :: Regexp -> String -> Int

matchTest :: Regexp -> String -> Bool

matchAllText :: Regexp -> String -> [MatchText String]

matchOnceText :: Regexp -> String -> Maybe (String, MatchText String, String)

RegexContext Regexp String String

Defined in Hledger.Utils.Regex

Methods

match :: Regexp -> String -> String

matchM :: MonadFail m => Regexp -> String -> m String

toRegex :: Text -> Either RegexError Regexp

toRegexCI :: Text -> Either RegexError Regexp

toRegex' :: Text -> Regexp

toRegexCI' :: Text -> Regexp

type aliases

type Replacement = String

A replacement pattern. May include numeric backreferences (N).

type RegexError = String

An error message arising during a regular expression operation. Eg: trying to compile a malformed regular expression, or trying to apply a malformed replacement pattern.

total regex operations

regexMatch :: Regexp -> String -> Bool

Test whether a Regexp matches a String. This is an alias for matchTest for consistent naming.

regexMatchText :: Regexp -> Text -> Bool

Tests whether a Regexp matches a Text.

This currently unpacks the Text to a String an works on that. This is due to a performance bug in regex-tdfa (#9), which may or may not be relevant here.

regexReplace :: Regexp -> Replacement -> String -> Either RegexError String

A memoising version of regexReplace. Caches the result for each search pattern, replacement pattern, target string tuple. This won't generate a regular expression parsing error since that is pre-compiled nowadays, but there can still be a runtime error from the replacement pattern, eg with a backreference referring to a nonexistent match group.

regexReplaceUnmemo :: Regexp -> Replacement -> String -> Either RegexError String

regexReplaceAllBy :: Regexp -> (String -> String) -> String -> String