Data.Text.ICU

text-icu-0.7.0.1: Bindings to the ICU library

Copyright | (c) 2010 Bryan O'Sullivan
License | BSD-style
Maintainer | bos@serpentine.com
Stability | experimental
Portability | GHC
Safe Haskell | None
Language | Haskell98

Data.Text.ICU

Contents

- Data representation
- Types
- Boundary analysis
- Case mapping
- Iteration
- Normalization
- String comparison
  - Normalization-sensitive string comparison
  - Locale-sensitive string collation
- Regular expressions
  - Construction
  - Inspection
  - Searching
  - Match groups

Description

Commonly used functions for Unicode, implemented as bindings to the International Components for Unicode (ICU) libraries.

This module contains only the most commonly used types and functions. Other modules in this package expose richer interfaces.

Synopsis

- data LocaleName
  - = Root
  - | Locale String
  - | Current
- data Breaker a
- data Break a
- brkPrefix :: Break a -> Text
- brkBreak :: Break a -> Text
- brkSuffix :: Break a -> Text
- brkStatus :: Break a -> a
- data Line
  - = Soft
  - | Hard
- data Word
  - = Uncategorized
  - | Number
  - | Letter
  - | Kana
  - | Ideograph
- breakCharacter :: LocaleName -> Breaker ()
- breakLine :: LocaleName -> Breaker Line
- breakSentence :: LocaleName -> Breaker ()
- breakWord :: LocaleName -> Breaker Word
- breaks :: Breaker a -> Text -> [Break a]
- breaksRight :: Breaker a -> Text -> [Break a]
- toCaseFold :: Bool -> Text -> Text
- toLower :: LocaleName -> Text -> Text
- toUpper :: LocaleName -> Text -> Text
- data CharIterator
- fromString :: String -> CharIterator
- fromText :: Text -> CharIterator
- fromUtf8 :: ByteString -> CharIterator
- data NormalizationMode
  - = None
  - | NFD
  - | NFKD
  - | NFC
  - | NFKC
  - | FCD
- normalize :: NormalizationMode -> Text -> Text
- quickCheck :: NormalizationMode -> Text -> Maybe Bool
- isNormalized :: NormalizationMode -> Text -> Bool
- data CompareOption
  - = InputIsFCD
  - | CompareIgnoreCase
  - | FoldCaseExcludeSpecialI
- compare :: [CompareOption] -> Text -> Text -> Ordering
- data Collator
- collator :: LocaleName -> Collator
- collatorWith :: LocaleName -> [Attribute] -> Collator
- collate :: Collator -> Text -> Text -> Ordering
- collateIter :: Collator -> CharIterator -> CharIterator -> Ordering
- sortKey :: Collator -> Text -> ByteString
- uca :: Collator
- data MatchOption
  - = CaseInsensitive
  - | Comments
  - | DotAll
  - | Literal
  - | Multiline
  - | HaskellLines
  - | UnicodeWord
  - | ErrorOnUnknownEscapes
  - | WorkLimit Int
  - | StackLimit Int
- data ParseError
- data Match
- data Regex
- class Regular r
- regex :: [MatchOption] -> Text -> Regex
- regex' :: [MatchOption] -> Text -> Either ParseError Regex
- pattern :: Regular r => r -> Text
- find :: Regex -> Text -> Maybe Match
- findAll :: Regex -> Text -> [Match]
- groupCount :: Regular r => r -> Int
- unfold :: (Int -> Match -> Maybe Text) -> Match -> [Text]
- span :: Match -> Text
- group :: Int -> Match -> Maybe Text
- prefix :: Int -> Match -> Maybe Text
- suffix :: Int -> Match -> Maybe Text

# Data representation

The Haskell `Text` type is implemented as an array in the Haskell heap. This means that its location is not pinned; it may be copied during a garbage collection pass. ICU, on the other hand, works with strings that are allocated in the normal system heap and have a fixed address.

To accommodate this need, these bindings use the functions from Data.Text.Foreign to copy data between the Haskell heap and the system heap. The copied strings are still managed automatically, but the need to duplicate data does add some performance and memory overhead.

# Types

data LocaleName #

The name of a locale.

Constructors

Root | The root locale. For a description of resource bundles and the root resource, see http://userguide.icu-project.org/locale/resources.
Locale String | A specific locale.
Current | The program's current locale.

Instances

Eq LocaleName # |
Methods (==) :: LocaleName -> LocaleName -> Bool # (/=) :: LocaleName -> LocaleName -> Bool #
Ord LocaleName # |
Methods compare :: LocaleName -> LocaleName -> Ordering # (<) :: LocaleName -> LocaleName -> Bool # (<=) :: LocaleName -> LocaleName -> Bool # (>) :: LocaleName -> LocaleName -> Bool # (>=) :: LocaleName -> LocaleName -> Bool # max :: LocaleName -> LocaleName -> LocaleName # min :: LocaleName -> LocaleName -> LocaleName #
Read LocaleName # |
Methods readsPrec :: Int -> ReadS LocaleName # readList :: ReadS [LocaleName] # readPrec :: ReadPrec LocaleName # readListPrec :: ReadPrec [LocaleName] #
Show LocaleName # |
Methods showsPrec :: Int -> LocaleName -> ShowS # show :: LocaleName -> String # showList :: [LocaleName] -> ShowS #
IsString LocaleName # |
Methods fromString :: String -> LocaleName #
NFData LocaleName # |
Methods rnf :: LocaleName -> () #

# Boundary analysis

Text boundary analysis is the process of locating linguistic boundaries while formatting and handling text. Examples of this process include:

- Locating appropriate points to word-wrap text to fit within specific margins while displaying or printing.
- Counting characters, words, sentences, or paragraphs.
- Making a list of the unique words in a document.
- Figuring out if a given range of text contains only whole words.
- Capitalizing the first letter of each word.
- Locating a particular unit of the text (For example, finding the third word in the document).

The `Breaker` type was designed to support these kinds of tasks.

For the impure boundary analysis API (which is richer, but less easy to use than the pure API), see the Data.Text.ICU.Break module. The impure API supports some uses that may be less efficient via the pure API, including:

- Locating the beginning of a word that the user has selected.
- Determining how far to move the text cursor when the user hits an arrow key (Some characters require more than one position in the text store and some characters in the text store do not display at all).

data Breaker a #

A boundary analyser.

data Break a #

A break in a string.

Instances

Eq a => Eq (Break a) # |
Methods (==) :: Break a -> Break a -> Bool # (/=) :: Break a -> Break a -> Bool #
Show a => Show (Break a) # |
Methods showsPrec :: Int -> Break a -> ShowS # show :: Break a -> String # showList :: [Break a] -> ShowS #
NFData a => NFData (Break a) # |
Methods rnf :: Break a -> () #

brkPrefix :: Break a -> Text #

Prefix of the current break.

brkBreak :: Break a -> Text #

Text of the current break.

brkSuffix :: Break a -> Text #

Suffix of the current break.

brkStatus :: Break a -> a #

Status of the current break (only meaningful if `Line` or `Word`).

data Line #

Line break status.

Constructors

Soft | A soft line break is a position at which a line break is acceptable, but not required.
Hard |

Instances

Enum Line # |
Methods succ :: Line -> Line # pred :: Line -> Line # toEnum :: Int -> Line # fromEnum :: Line -> Int # enumFrom :: Line -> [Line] # enumFromThen :: Line -> Line -> [Line] # enumFromTo :: Line -> Line -> [Line] # enumFromThenTo :: Line -> Line -> Line -> [Line] #
Eq Line # |
Methods (==) :: Line -> Line -> Bool # (/=) :: Line -> Line -> Bool #
Show Line # |
Methods showsPrec :: Int -> Line -> ShowS # show :: Line -> String # showList :: [Line] -> ShowS #
NFData Line # |
Methods rnf :: Line -> () #

data Word #

Word break status.

Constructors

Uncategorized | A "word" that does not fit into another category. Includes spaces and most punctuation.
Number | A word that appears to be a number.
Letter | A word containing letters, excluding hiragana, katakana or ideographic characters.
Kana | A word containing kana characters.
Ideograph | A word containing ideographic characters.

Instances

Enum Word # |
Methods succ :: Word -> Word # pred :: Word -> Word # toEnum :: Int -> Word # fromEnum :: Word -> Int # enumFrom :: Word -> [Word] # enumFromThen :: Word -> Word -> [Word] # enumFromTo :: Word -> Word -> [Word] # enumFromThenTo :: Word -> Word -> Word -> [Word] #
Eq Word # |
Methods (==) :: Word -> Word -> Bool # (/=) :: Word -> Word -> Bool #
Show Word # |
Methods showsPrec :: Int -> Word -> ShowS # show :: Word -> String # showList :: [Word] -> ShowS #
NFData Word # |
Methods rnf :: Word -> () #

breakCharacter :: LocaleName -> Breaker () #

Break a string on character boundaries.

Character boundary analysis identifies the boundaries of "Extended Grapheme Clusters", which are groupings of codepoints that should be treated as character-like units for many text operations. Please see Unicode Standard Annex #29, Unicode Text Segmentation, http://www.unicode.org/reports/tr29/ for additional information on grapheme clusters and guidelines on their use.

breakLine :: LocaleName -> Breaker Line #

Break a string on line boundaries.

Line boundary analysis determines where a text string can be broken when line wrapping. The mechanism correctly handles punctuation and hyphenated words.

breakSentence :: LocaleName -> Breaker () #

Break a string on sentence boundaries.

Sentence boundary analysis allows selection with correct interpretation of periods within numbers and abbreviations, and trailing punctuation marks such as quotation marks and parentheses.

breakWord :: LocaleName -> Breaker Word #

Break a string on word boundaries.

Word boundary analysis is used by search and replace functions, as well as within text editing applications that allow the user to select words with a double click. Word selection provides correct interpretation of punctuation marks within and following words. Characters that are not part of a word, such as symbols or punctuation marks, have word breaks on both sides.

breaks :: Breaker a -> Text -> [Break a] #

Return a list of all breaks in a string, from left to right.

breaksRight :: Breaker a -> Text -> [Break a] #

Return a list of all breaks in a string, from right to left.

# Case mapping

toCaseFold #

Arguments

:: Bool | Whether to include or exclude mappings for dotted and dotless I and i that are marked with `I` in `CaseFolding.txt`.
-> Text |
-> Text |

Case-fold the characters in a string.

Case folding is locale independent and not context sensitive, but there is an option for treating the letter I specially for Turkic languages. The result may be longer or shorter than the original.

toLower :: LocaleName -> Text -> Text #

Lowercase the characters in a string.

Casing is locale dependent and context sensitive. The result may be longer or shorter than the original.

toUpper :: LocaleName -> Text -> Text #

Uppercase the characters in a string.

Casing is locale dependent and context sensitive. The result may be longer or shorter than the original.

# Iteration

data CharIterator #

A type that supports efficient iteration over Unicode characters.

As an example of where this may be useful, a function using this type may be able to iterate over a UTF-8 `ByteString` directly, rather than first copying and converting it to an intermediate form. This type also allows e.g. comparison between `Text` and `ByteString`, with minimal overhead.

Instances

Show CharIterator # |
Methods showsPrec :: Int -> CharIterator -> ShowS # show :: CharIterator -> String # showList :: [CharIterator] -> ShowS #

fromString :: String -> CharIterator #

Construct a `CharIterator` from a Unicode string.

fromText :: Text -> CharIterator #

Construct a `CharIterator` from a Unicode string.

fromUtf8 :: ByteString -> CharIterator #

Construct a `CharIterator` from a Unicode string encoded as a UTF-8 `ByteString`. The validity of the encoded string is *not* checked.

# Normalization

data NormalizationMode #

Normalization modes.

Constructors

None | No decomposition/composition.
NFD | Canonical decomposition.
NFKD | Compatibility decomposition.
NFC | Canonical decomposition followed by canonical composition.
NFKC | Compatibility decomposition followed by canonical composition.
FCD | "Fast C or D" form.

Instances

Enum NormalizationMode # |
Methods succ :: NormalizationMode -> NormalizationMode # pred :: NormalizationMode -> NormalizationMode # toEnum :: Int -> NormalizationMode # fromEnum :: NormalizationMode -> Int # enumFrom :: NormalizationMode -> [NormalizationMode] # enumFromThen :: NormalizationMode -> NormalizationMode -> [NormalizationMode] # enumFromTo :: NormalizationMode -> NormalizationMode -> [NormalizationMode] # enumFromThenTo :: NormalizationMode -> NormalizationMode -> NormalizationMode -> [NormalizationMode] #
Eq NormalizationMode # |
Methods (==) :: NormalizationMode -> NormalizationMode -> Bool # (/=) :: NormalizationMode -> NormalizationMode -> Bool #
Show NormalizationMode # |
Methods showsPrec :: Int -> NormalizationMode -> ShowS # show :: NormalizationMode -> String # showList :: [NormalizationMode] -> ShowS #

normalize :: NormalizationMode -> Text -> Text #

Normalize a string according the specified normalization mode.

quickCheck :: NormalizationMode -> Text -> Maybe Bool #

Perform an efficient check on a string, to quickly determine if the string is in a particular normalization form.

A `Nothing` result indicates that a definite answer could not be determined quickly, and a more thorough check is required, e.g. with `isNormalized`. The user may have to convert the string to its normalized form and compare the results.

A result of `Just` `True` or `Just` `False` indicates that the string definitely is, or is not, in the given normalization form.

isNormalized :: NormalizationMode -> Text -> Bool #

Indicate whether a string is in a given normalization form.

Unlike `quickCheck`, this function returns a definitive result. For `NFD`, `NFKD`, and `FCD` normalization forms, both functions work in exactly the same ways. For `NFC` and `NFKC` forms, where `quickCheck` may return `Nothing`, this function will perform further tests to arrive at a definitive result.

# String comparison

## Normalization-sensitive string comparison

data CompareOption #

Options to `compare`.

Constructors

InputIsFCD | The caller knows that both strings fulfill the `FCD` conditions. If not set, `compare` will `quickCheck` for `FCD` and normalize if necessary.
CompareIgnoreCase | Compare strings case-insensitively using case folding, instead of case-sensitively. If set, then the following case folding options are used.
FoldCaseExcludeSpecialI | When case folding, exclude the special I character. For use with Turkic (Turkish/Azerbaijani) text data.

Instances

Enum CompareOption # |
Methods succ :: CompareOption -> CompareOption # pred :: CompareOption -> CompareOption # toEnum :: Int -> CompareOption # fromEnum :: CompareOption -> Int # enumFrom :: CompareOption -> [CompareOption] # enumFromThen :: CompareOption -> CompareOption -> [CompareOption] # enumFromTo :: CompareOption -> CompareOption -> [CompareOption] # enumFromThenTo :: CompareOption -> CompareOption -> CompareOption -> [CompareOption] #
Eq CompareOption # |
Methods (==) :: CompareOption -> CompareOption -> Bool # (/=) :: CompareOption -> CompareOption -> Bool #
Show CompareOption # |
Methods showsPrec :: Int -> CompareOption -> ShowS # show :: CompareOption -> String # showList :: [CompareOption] -> ShowS #

compare :: [CompareOption] -> Text -> Text -> Ordering #

Compare two strings for canonical equivalence. Further options include case-insensitive comparison and code point order (as opposed to code unit order).

Canonical equivalence between two strings is defined as their normalized forms (`NFD` or `NFC`) being identical. This function compares strings incrementally instead of normalizing (and optionally case-folding) both strings entirely, improving performance significantly.

Bulk normalization is only necessary if the strings do not fulfill the `FCD` conditions. Only in this case, and only if the strings are relatively long, is memory allocated temporarily. For `FCD` strings and short non-`FCD` strings there is no memory allocation.

## Locale-sensitive string collation

For the impure collation API (which is richer, but less easy to use than the pure API), see the Data.Text.ICU.Collate module.

data Collator #

String collator type. `Collator`s are considered equal if they will sort strings identically.

collator :: LocaleName -> Collator #

Create an immutable `Collator` for comparing strings.

If `Root` is passed as the locale, UCA collation rules will be used.

collatorWith :: LocaleName -> [Attribute] -> Collator #

Create an immutable `Collator` with the given `Attribute`s.

collate :: Collator -> Text -> Text -> Ordering #

Compare two strings.

collateIter :: Collator -> CharIterator -> CharIterator -> Ordering #

Compare two `CharIterator`s.

If either iterator was constructed from a `ByteString`, it does not need to be copied or converted beforehand, so this function can be quite cheap.

sortKey :: Collator -> Text -> ByteString #

Create a key for sorting the `Text` using the given `Collator`. The result of comparing two `ByteString`s that have been transformed with `sortKey` will be the same as the result of `collate` on the two untransformed `Text`s.

uca :: Collator #

A `Collator` that uses the Unicode Collation Algorithm (UCA).

# Regular expressions

data MatchOption #

Options for controlling matching behaviour.

Constructors

CaseInsensitive | Enable case insensitive matching.
Comments | Allow comments and white space within patterns.
DotAll | If set, `'.'` matches line terminators. Otherwise `'.'` matching stops at line end.
Literal | If set, treat the entire pattern as a literal string. Metacharacters or escape sequences in the input sequence will be given no special meaning. The option `CaseInsensitive` retains its meanings on matching when used in conjunction with this option. Other options become superfluous.
Multiline | Control behaviour of `'$'` and `'^'`. If set, recognize line terminators within string, Otherwise, match only at start and end of input string.
HaskellLines | Haskell-only line endings. When this mode is enabled, only `'\n'` is recognized as a line ending in the behavior of `'.'`, `'^'`, and `'$'`.
UnicodeWord | Unicode word boundaries. If set, `'\\b'` uses the Unicode TR 29 definition of word boundaries. Warning: Unicode word boundaries are quite different from traditional regular expression word boundaries. See http://unicode.org/reports/tr29/#Word_Boundaries.
ErrorOnUnknownEscapes | Throw an error on unrecognized backslash escapes. If set, fail with an error on patterns that contain backslash-escaped ASCII letters without a known special meaning. If this flag is not set, these escaped letters represent themselves.
WorkLimit Int | Set a processing limit for match operations. Some patterns, when matching certain strings, can run in exponential time. For practical purposes, the match operation may appear to be in an infinite loop. When a limit is set a match operation will fail with an error if the limit is exceeded. The units of the limit are steps of the match engine. Correspondence with actual processor time will depend on the speed of the processor and the details of the specific pattern, but will typically be on the order of milliseconds. By default, the matching time is not limited.
StackLimit Int | Set the amount of heap storage avaliable for use by the match backtracking stack. ICU uses a backtracking regular expression engine, with the backtrack stack maintained on the heap. This function sets the limit to the amount of memory that can be used for this purpose. A backtracking stack overflow will result in an error from the match operation that caused it. A limit is desirable because a malicious or poorly designed pattern can use excessive memory, potentially crashing the process. A limit is enabled by default.

Instances

Eq MatchOption # |
Methods (==) :: MatchOption -> MatchOption -> Bool # (/=) :: MatchOption -> MatchOption -> Bool #
Show MatchOption # |
Methods showsPrec :: Int -> MatchOption -> ShowS # show :: MatchOption -> String # showList :: [MatchOption] -> ShowS #

data ParseError #

Detailed information about parsing errors. Used by ICU parsing engines that parse long rules, patterns, or programs, where the text being parsed is long enough that more information than an `ICUError` is needed to localize the error.

Instances

Show ParseError # |
Methods showsPrec :: Int -> ParseError -> ShowS # show :: ParseError -> String # showList :: [ParseError] -> ShowS #
Exception ParseError # |
Methods toException :: ParseError -> SomeException # fromException :: SomeException -> Maybe ParseError # displayException :: ParseError -> String #
NFData ParseError # |
Methods rnf :: ParseError -> () #

data Match #

A match for a regular expression.

Instances

Show Match # |
Methods showsPrec :: Int -> Match -> ShowS # show :: Match -> String # showList :: [Match] -> ShowS #
Regular Match # |
Methods regRe :: Match -> Regex regFp :: Match -> ForeignPtr URegularExpression

data Regex #

A compiled regular expression.

`Regex` values are usually constructed using the `regex` or `regex'` functions. This type is also an instance of `IsString`, so if you have the `OverloadedStrings` language extension enabled, you can construct a `Regex` by simply writing the pattern in quotes (though this does not allow you to specify any `Option`s).

Instances

Show Regex # |
Methods showsPrec :: Int -> Regex -> ShowS # show :: Regex -> String # showList :: [Regex] -> ShowS #
IsString Regex # |
Methods fromString :: String -> Regex #
Regular Regex # |
Methods regRe :: Regex -> Regex regFp :: Regex -> ForeignPtr URegularExpression

class Regular r #

A typeclass for functions common to both `Match` and `Regex` types.

Minimal complete definition

regRe

Instances

Regular Match # |
Methods regRe :: Match -> Regex regFp :: Match -> ForeignPtr URegularExpression
Regular Regex # |
Methods regRe :: Regex -> Regex regFp :: Regex -> ForeignPtr URegularExpression

## Construction

regex :: [MatchOption] -> Text -> Regex #

Compile a regular expression with the given options. This function throws a `ParseError` if the pattern is invalid, so it is best for use when the pattern is statically known.

regex' :: [MatchOption] -> Text -> Either ParseError Regex #

Compile a regular expression with the given options. This is safest to use when the pattern is constructed at run time.

## Inspection

pattern :: Regular r => r -> Text #

Return the source form of the pattern used to construct this regular expression or match.

## Searching

find :: Regex -> Text -> Maybe Match #

Find the first match for the regular expression in the given text.

findAll :: Regex -> Text -> [Match] #

Lazily find all matches for the regular expression in the given text.

## Match groups

Capturing groups are numbered starting from zero. Group zero is always the entire matching text. Groups greater than zero contain the text matching each capturing group in a regular expression.

groupCount :: Regular r => r -> Int #

Return the number of capturing groups in this regular expression or match's pattern.

unfold :: (Int -> Match -> Maybe Text) -> Match -> [Text] #

A combinator for returning a list of all capturing groups on a `Match`.

span :: Match -> Text #

Return the span of text between the end of the previous match and the beginning of the current match.

group :: Int -> Match -> Maybe Text #

Return the nth capturing group in a match, or `Nothing` if n is out of bounds.

prefix :: Int -> Match -> Maybe Text #

Return the prefix of the nth capturing group in a match (the text from the start of the string to the start of the match), or `Nothing` if n is out of bounds.

suffix :: Int -> Match -> Maybe Text #

Return the suffix of the nth capturing group in a match (the text from the end of the match to the end of the string), or `Nothing` if n is out of bounds.