base-4.12.0.0: Basic libraries

Copyright(c) The University of Glasgow 2001
LicenseBSD-style (see the file libraries/base/LICENSE)
Maintainerlibraries@haskell.org
Stabilitystable
Portabilityportable
Safe HaskellTrustworthy
LanguageHaskell2010

Data.Char

Contents

Description

The Char type and associated operations.

Synopsis

Documentation

data Char Source #

The character type Char is an enumeration whose values represent Unicode (or equivalently ISO/IEC 10646) code points (i.e. characters, see http://www.unicode.org/ for details). This set extends the ISO 8859-1 (Latin-1) character set (the first 256 characters), which is itself an extension of the ASCII character set (the first 128 characters). A character literal in Haskell has type Char.

To convert a Char to or from the corresponding Int value defined by Unicode, use toEnum and fromEnum from the Enum class respectively (or equivalently ord and chr).

Instances
Bounded Char Source #

Since: 2.1

Instance details

Defined in GHC.Enum

Enum Char Source #

Since: 2.1

Instance details

Defined in GHC.Enum

Eq Char 
Instance details

Defined in GHC.Classes

Methods

(==) :: Char -> Char -> Bool Source #

(/=) :: Char -> Char -> Bool Source #

Data Char Source #

Since: 4.0.0.0

Instance details

Defined in Data.Data

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Char -> c Char Source #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Char Source #

toConstr :: Char -> Constr Source #

dataTypeOf :: Char -> DataType Source #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Char) Source #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Char) Source #

gmapT :: (forall b. Data b => b -> b) -> Char -> Char Source #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Char -> r Source #

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Char -> r Source #

gmapQ :: (forall d. Data d => d -> u) -> Char -> [u] Source #

gmapQi :: Int -> (forall d. Data d => d -> u) -> Char -> u Source #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Char -> m Char Source #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Char -> m Char Source #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Char -> m Char Source #

Ord Char 
Instance details

Defined in GHC.Classes

Read Char Source #

Since: 2.1

Instance details

Defined in GHC.Read

Show Char Source #

Since: 2.1

Instance details

Defined in GHC.Show

Ix Char Source #

Since: 2.1

Instance details

Defined in GHC.Arr

Storable Char Source #

Since: 2.1

Instance details

Defined in Foreign.Storable

IsChar Char Source #

Since: 2.1

Instance details

Defined in Text.Printf

PrintfArg Char Source #

Since: 2.1

Instance details

Defined in Text.Printf

Generic1 (URec Char :: k -> Type) Source # 
Instance details

Defined in GHC.Generics

Associated Types

type Rep1 (URec Char) :: k -> Type Source #

Methods

from1 :: URec Char a -> Rep1 (URec Char) a Source #

to1 :: Rep1 (URec Char) a -> URec Char a Source #

Functor (URec Char :: Type -> Type) Source #

Since: 4.9.0.0

Instance details

Defined in GHC.Generics

Methods

fmap :: (a -> b) -> URec Char a -> URec Char b Source #

(<$) :: a -> URec Char b -> URec Char a Source #

Foldable (URec Char :: Type -> Type) Source #

Since: 4.9.0.0

Instance details

Defined in Data.Foldable

Methods

fold :: Monoid m => URec Char m -> m Source #

foldMap :: Monoid m => (a -> m) -> URec Char a -> m Source #

foldr :: (a -> b -> b) -> b -> URec Char a -> b Source #

foldr' :: (a -> b -> b) -> b -> URec Char a -> b Source #

foldl :: (b -> a -> b) -> b -> URec Char a -> b Source #

foldl' :: (b -> a -> b) -> b -> URec Char a -> b Source #

foldr1 :: (a -> a -> a) -> URec Char a -> a Source #

foldl1 :: (a -> a -> a) -> URec Char a -> a Source #

toList :: URec Char a -> [a] Source #

null :: URec Char a -> Bool Source #

length :: URec Char a -> Int Source #

elem :: Eq a => a -> URec Char a -> Bool Source #

maximum :: Ord a => URec Char a -> a Source #

minimum :: Ord a => URec Char a -> a Source #

sum :: Num a => URec Char a -> a Source #

product :: Num a => URec Char a -> a Source #

Traversable (URec Char :: Type -> Type) Source #

Since: 4.9.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> URec Char a -> f (URec Char b) Source #

sequenceA :: Applicative f => URec Char (f a) -> f (URec Char a) Source #

mapM :: Monad m => (a -> m b) -> URec Char a -> m (URec Char b) Source #

sequence :: Monad m => URec Char (m a) -> m (URec Char a) Source #

Eq (URec Char p) Source #

Since: 4.9.0.0

Instance details

Defined in GHC.Generics

Methods

(==) :: URec Char p -> URec Char p -> Bool Source #

(/=) :: URec Char p -> URec Char p -> Bool Source #

Ord (URec Char p) Source #

Since: 4.9.0.0

Instance details

Defined in GHC.Generics

Methods

compare :: URec Char p -> URec Char p -> Ordering Source #

(<) :: URec Char p -> URec Char p -> Bool Source #

(<=) :: URec Char p -> URec Char p -> Bool Source #

(>) :: URec Char p -> URec Char p -> Bool Source #

(>=) :: URec Char p -> URec Char p -> Bool Source #

max :: URec Char p -> URec Char p -> URec Char p Source #

min :: URec Char p -> URec Char p -> URec Char p Source #

Show (URec Char p) Source #

Since: 4.9.0.0

Instance details

Defined in GHC.Generics

Generic (URec Char p) Source # 
Instance details

Defined in GHC.Generics

Associated Types

type Rep (URec Char p) :: Type -> Type Source #

Methods

from :: URec Char p -> Rep (URec Char p) x Source #

to :: Rep (URec Char p) x -> URec Char p Source #

data URec Char (p :: k) Source #

Used for marking occurrences of Char#

Since: 4.9.0.0

Instance details

Defined in GHC.Generics

data URec Char (p :: k) = UChar {}
type Rep1 (URec Char :: k -> Type) Source #

Since: 4.9.0.0

Instance details

Defined in GHC.Generics

type Rep1 (URec Char :: k -> Type) = D1 (MetaData "URec" "GHC.Generics" "base" False) (C1 (MetaCons "UChar" PrefixI True) (S1 (MetaSel (Just "uChar#") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (UChar :: k -> Type)))
type Rep (URec Char p) Source #

Since: 4.9.0.0

Instance details

Defined in GHC.Generics

type Rep (URec Char p) = D1 (MetaData "URec" "GHC.Generics" "base" False) (C1 (MetaCons "UChar" PrefixI True) (S1 (MetaSel (Just "uChar#") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (UChar :: Type -> Type)))

Character classification

Unicode characters are divided into letters, numbers, marks, punctuation, symbols, separators (including spaces) and others (including control characters).

isControl :: Char -> Bool Source #

Selects control characters, which are the non-printing characters of the Latin-1 subset of Unicode.

isSpace :: Char -> Bool Source #

Returns True for any Unicode space character, and the control characters \t, \n, \r, \f, \v.

isLower :: Char -> Bool Source #

Selects lower-case alphabetic Unicode characters (letters).

isUpper :: Char -> Bool Source #

Selects upper-case or title-case alphabetic Unicode characters (letters). Title case is used by a small number of letter ligatures like the single-character form of Lj.

isAlpha :: Char -> Bool Source #

Selects alphabetic Unicode characters (lower-case, upper-case and title-case letters, plus letters of caseless scripts and modifiers letters). This function is equivalent to isLetter.

isAlphaNum :: Char -> Bool Source #

Selects alphabetic or numeric Unicode characters.

Note that numeric digits outside the ASCII range, as well as numeric characters which aren't digits, are selected by this function but not by isDigit. Such characters may be part of identifiers but are not used by the printer and reader to represent numbers.

isPrint :: Char -> Bool Source #

Selects printable Unicode characters (letters, numbers, marks, punctuation, symbols and spaces).

isDigit :: Char -> Bool Source #

Selects ASCII digits, i.e. '0'..'9'.

isOctDigit :: Char -> Bool Source #

Selects ASCII octal digits, i.e. '0'..'7'.

isHexDigit :: Char -> Bool Source #

Selects ASCII hexadecimal digits, i.e. '0'..'9', 'a'..'f', 'A'..'F'.

isLetter :: Char -> Bool Source #

Selects alphabetic Unicode characters (lower-case, upper-case and title-case letters, plus letters of caseless scripts and modifiers letters). This function is equivalent to isAlpha.

This function returns True if its argument has one of the following GeneralCategorys, or False otherwise:

These classes are defined in the Unicode Character Database, part of the Unicode standard. The same document defines what is and is not a "Letter".

Examples

Expand

Basic usage:

>>> isLetter 'a'
True
>>> isLetter 'A'
True
>>> isLetter 'λ'
True
>>> isLetter '0'
False
>>> isLetter '%'
False
>>> isLetter '♥'
False
>>> isLetter '\31'
False

Ensure that isLetter and isAlpha are equivalent.

>>> let chars = [(chr 0)..]
>>> let letters = map isLetter chars
>>> let alphas = map isAlpha chars
>>> letters == alphas
True

isMark :: Char -> Bool Source #

Selects Unicode mark characters, for example accents and the like, which combine with preceding characters.

This function returns True if its argument has one of the following GeneralCategorys, or False otherwise:

These classes are defined in the Unicode Character Database, part of the Unicode standard. The same document defines what is and is not a "Mark".

Examples

Expand

Basic usage:

>>> isMark 'a'
False
>>> isMark '0'
False

Combining marks such as accent characters usually need to follow another character before they become printable:

>>> map isMark "ò"
[False,True]

Puns are not necessarily supported:

>>> isMark '✓'
False

isNumber :: Char -> Bool Source #

Selects Unicode numeric characters, including digits from various scripts, Roman numerals, et cetera.

This function returns True if its argument has one of the following GeneralCategorys, or False otherwise:

These classes are defined in the Unicode Character Database, part of the Unicode standard. The same document defines what is and is not a "Number".

Examples

Expand

Basic usage:

>>> isNumber 'a'
False
>>> isNumber '%'
False
>>> isNumber '3'
True

ASCII '0' through '9' are all numbers:

>>> and $ map isNumber ['0'..'9']
True

Unicode Roman numerals are "numbers" as well:

>>> isNumber 'Ⅸ'
True

isPunctuation :: Char -> Bool Source #

Selects Unicode punctuation characters, including various kinds of connectors, brackets and quotes.

This function returns True if its argument has one of the following GeneralCategorys, or False otherwise:

These classes are defined in the Unicode Character Database, part of the Unicode standard. The same document defines what is and is not a "Punctuation".

Examples

Expand

Basic usage:

>>> isPunctuation 'a'
False
>>> isPunctuation '7'
False
>>> isPunctuation '♥'
False
>>> isPunctuation '"'
True
>>> isPunctuation '?'
True
>>> isPunctuation '—'
True

isSymbol :: Char -> Bool Source #

Selects Unicode symbol characters, including mathematical and currency symbols.

This function returns True if its argument has one of the following GeneralCategorys, or False otherwise:

These classes are defined in the Unicode Character Database, part of the Unicode standard. The same document defines what is and is not a "Symbol".

Examples

Expand

Basic usage:

>>> isSymbol 'a'
False
>>> isSymbol '6'
False
>>> isSymbol '='
True

The definition of "math symbol" may be a little counter-intuitive depending on one's background:

>>> isSymbol '+'
True
>>> isSymbol '-'
False

isSeparator :: Char -> Bool Source #

Selects Unicode space and separator characters.

This function returns True if its argument has one of the following GeneralCategorys, or False otherwise:

These classes are defined in the Unicode Character Database, part of the Unicode standard. The same document defines what is and is not a "Separator".

Examples

Expand

Basic usage:

>>> isSeparator 'a'
False
>>> isSeparator '6'
False
>>> isSeparator ' '
True

Warning: newlines and tab characters are not considered separators.

>>> isSeparator '\n'
False
>>> isSeparator '\t'
False

But some more exotic characters are (like HTML's &nbsp;):

>>> isSeparator '\160'
True

Subranges

isAscii :: Char -> Bool Source #

Selects the first 128 characters of the Unicode character set, corresponding to the ASCII character set.

isLatin1 :: Char -> Bool Source #

Selects the first 256 characters of the Unicode character set, corresponding to the ISO 8859-1 (Latin-1) character set.

isAsciiUpper :: Char -> Bool Source #

Selects ASCII upper-case letters, i.e. characters satisfying both isAscii and isUpper.

isAsciiLower :: Char -> Bool Source #

Selects ASCII lower-case letters, i.e. characters satisfying both isAscii and isLower.

Unicode general categories

data GeneralCategory Source #

Unicode General Categories (column 2 of the UnicodeData table) in the order they are listed in the Unicode standard (the Unicode Character Database, in particular).

Examples

Expand

Basic usage:

>>> :t OtherLetter
OtherLetter :: GeneralCategory

Eq instance:

>>> UppercaseLetter == UppercaseLetter
True
>>> UppercaseLetter == LowercaseLetter
False

Ord instance:

>>> NonSpacingMark <= MathSymbol
True

Enum instance:

>>> enumFromTo ModifierLetter SpacingCombiningMark
[ModifierLetter,OtherLetter,NonSpacingMark,SpacingCombiningMark]

Read instance:

>>> read "DashPunctuation" :: GeneralCategory
DashPunctuation
>>> read "17" :: GeneralCategory
*** Exception: Prelude.read: no parse

Show instance:

>>> show EnclosingMark
"EnclosingMark"

Bounded instance:

>>> minBound :: GeneralCategory
UppercaseLetter
>>> maxBound :: GeneralCategory
NotAssigned

Ix instance:

>>> import Data.Ix ( index )
>>> index (OtherLetter,Control) FinalQuote
12
>>> index (OtherLetter,Control) Format
*** Exception: Error in array index

Constructors

UppercaseLetter

Lu: Letter, Uppercase

LowercaseLetter

Ll: Letter, Lowercase

TitlecaseLetter

Lt: Letter, Titlecase

ModifierLetter

Lm: Letter, Modifier

OtherLetter

Lo: Letter, Other

NonSpacingMark

Mn: Mark, Non-Spacing

SpacingCombiningMark

Mc: Mark, Spacing Combining

EnclosingMark

Me: Mark, Enclosing

DecimalNumber

Nd: Number, Decimal

LetterNumber

Nl: Number, Letter

OtherNumber

No: Number, Other

ConnectorPunctuation

Pc: Punctuation, Connector

DashPunctuation

Pd: Punctuation, Dash

OpenPunctuation

Ps: Punctuation, Open

ClosePunctuation

Pe: Punctuation, Close

InitialQuote

Pi: Punctuation, Initial quote

FinalQuote

Pf: Punctuation, Final quote

OtherPunctuation

Po: Punctuation, Other

MathSymbol

Sm: Symbol, Math

CurrencySymbol

Sc: Symbol, Currency

ModifierSymbol

Sk: Symbol, Modifier

OtherSymbol

So: Symbol, Other

Space

Zs: Separator, Space

LineSeparator

Zl: Separator, Line

ParagraphSeparator

Zp: Separator, Paragraph

Control

Cc: Other, Control

Format

Cf: Other, Format

Surrogate

Cs: Other, Surrogate

PrivateUse

Co: Other, Private Use

NotAssigned

Cn: Other, Not Assigned

Instances
Bounded GeneralCategory Source #

Since: 2.1

Instance details

Defined in GHC.Unicode

Enum GeneralCategory Source #

Since: 2.1

Instance details

Defined in GHC.Unicode

Eq GeneralCategory Source #

Since: 2.1

Instance details

Defined in GHC.Unicode

Ord GeneralCategory Source #

Since: 2.1

Instance details

Defined in GHC.Unicode

Read GeneralCategory Source #

Since: 2.1

Instance details

Defined in GHC.Read

Show GeneralCategory Source #

Since: 2.1

Instance details

Defined in GHC.Unicode

Ix GeneralCategory Source #

Since: 2.1

Instance details

Defined in GHC.Unicode

generalCategory :: Char -> GeneralCategory Source #

The Unicode general category of the character. This relies on the Enum instance of GeneralCategory, which must remain in the same order as the categories are presented in the Unicode standard.

Examples

Expand

Basic usage:

>>> generalCategory 'a'
LowercaseLetter
>>> generalCategory 'A'
UppercaseLetter
>>> generalCategory '0'
DecimalNumber
>>> generalCategory '%'
OtherPunctuation
>>> generalCategory '♥'
OtherSymbol
>>> generalCategory '\31'
Control
>>> generalCategory ' '
Space

Case conversion

toUpper :: Char -> Char Source #

Convert a letter to the corresponding upper-case letter, if any. Any other character is returned unchanged.

toLower :: Char -> Char Source #

Convert a letter to the corresponding lower-case letter, if any. Any other character is returned unchanged.

toTitle :: Char -> Char Source #

Convert a letter to the corresponding title-case or upper-case letter, if any. (Title case differs from upper case only for a small number of ligature letters.) Any other character is returned unchanged.

Single digit characters

digitToInt :: Char -> Int Source #

Convert a single digit Char to the corresponding Int. This function fails unless its argument satisfies isHexDigit, but recognises both upper- and lower-case hexadecimal digits (that is, '0'..'9', 'a'..'f', 'A'..'F').

Examples

Expand

Characters '0' through '9' are converted properly to 0..9:

>>> map digitToInt ['0'..'9']
[0,1,2,3,4,5,6,7,8,9]

Both upper- and lower-case 'A' through 'F' are converted as well, to 10..15.

>>> map digitToInt ['a'..'f']
[10,11,12,13,14,15]
>>> map digitToInt ['A'..'F']
[10,11,12,13,14,15]

Anything else throws an exception:

>>> digitToInt 'G'
*** Exception: Char.digitToInt: not a digit 'G'
>>> digitToInt '♥'
*** Exception: Char.digitToInt: not a digit '\9829'

intToDigit :: Int -> Char Source #

Convert an Int in the range 0..15 to the corresponding single digit Char. This function fails on other inputs, and generates lower-case hexadecimal digits.

Numeric representations

ord :: Char -> Int Source #

The fromEnum method restricted to the type Char.

chr :: Int -> Char Source #

The toEnum method restricted to the type Char.

String representations

showLitChar :: Char -> ShowS Source #

Convert a character to a string using only printable characters, using Haskell source-language escape conventions. For example:

showLitChar '\n' s  =  "\\n" ++ s

lexLitChar :: ReadS String Source #

Read a string representation of a character, using Haskell source-language escape conventions. For example:

lexLitChar  "\\nHello"  =  [("\\n", "Hello")]

readLitChar :: ReadS Char Source #

Read a string representation of a character, using Haskell source-language escape conventions, and convert it to the character that it encodes. For example:

readLitChar "\\nHello"  =  [('\n', "Hello")]