| base-3.0.0.0: Basic libraries | Contents | Index

Data.Char |

Portability | portable
Stability | stable
Maintainer | libraries@haskell.org

Contents

Character classification
  Subranges
  Unicode general categories
Case conversion
Single digit characters
Numeric representations
String representations

Description
The Char type and associated operations.
Synopsis

data Char
type String = [Char]
isControl :: Char -> Bool
isSpace :: Char -> Bool
isLower :: Char -> Bool
isUpper :: Char -> Bool
isAlpha :: Char -> Bool
isAlphaNum :: Char -> Bool
isPrint :: Char -> Bool
isDigit :: Char -> Bool
isOctDigit :: Char -> Bool
isHexDigit :: Char -> Bool
isLetter :: Char -> Bool
isMark :: Char -> Bool
isNumber :: Char -> Bool
isPunctuation :: Char -> Bool
isSymbol :: Char -> Bool
isSeparator :: Char -> Bool
isAscii :: Char -> Bool
isLatin1 :: Char -> Bool
isAsciiUpper :: Char -> Bool
isAsciiLower :: Char -> Bool

data GeneralCategory

= UppercaseLetter
| LowercaseLetter
| TitlecaseLetter
| ModifierLetter
| OtherLetter
| NonSpacingMark
| SpacingCombiningMark
| EnclosingMark
| DecimalNumber
| LetterNumber
| OtherNumber
| ConnectorPunctuation
| DashPunctuation
| OpenPunctuation
| ClosePunctuation
| InitialQuote
| FinalQuote
| OtherPunctuation
| MathSymbol
| CurrencySymbol
| ModifierSymbol
| OtherSymbol
| Space
| LineSeparator
| ParagraphSeparator
| Control
| Format
| Surrogate
| PrivateUse
| NotAssigned

generalCategory :: Char -> GeneralCategory
toUpper :: Char -> Char
toLower :: Char -> Char
toTitle :: Char -> Char
digitToInt :: Char -> Int
intToDigit :: Int -> Char
ord :: Char -> Int
chr :: Int -> Char
showLitChar :: Char -> ShowS
lexLitChar :: ReadS String
readLitChar :: ReadS Char

Documentation
data Char

The character type `Char` is an enumeration whose values represent Unicode (or equivalently ISO/IEC 10646) characters (see http://www.unicode.org/ for details). This set extends the ISO 8859-1 (Latin-1) character set (the first 256 charachers), 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
Data Char
Enum Char
Eq Char
IsChar Char
Ix Char
Ord Char
PrintfArg Char
Read Char
Show Char
Storable Char
Typeable Char
IsString [Char]

type String = [Char]
A `String` is a list of characters. String constants in Haskell are values of type `String`.
Character classification
Unicode characters are divided into letters, numbers, marks, punctuation, symbols, separators (including spaces) and others (including control characters).
isControl :: Char -> Bool
Selects control characters, which are the non-printing characters of the Latin-1 subset of Unicode.
isSpace :: Char -> Bool
Selects white-space characters in the Latin-1 range. (In Unicode terms, this includes spaces and some control characters.)
isLower :: Char -> Bool
Selects lower-case alphabetic Unicode characters (letters).
isUpper :: Char -> Bool
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
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
Selects alphabetic or numeric digit Unicode characters. Note that numeric digits outside the ASCII range are selected by this function but not by `isDigit`. Such digits may be part of identifiers but are not used by the printer and reader to represent numbers.
isPrint :: Char -> Bool
Selects printable Unicode characters (letters, numbers, marks, punctuation, symbols and spaces).
isDigit :: Char -> Bool
Selects ASCII digits, i.e. `'0'`..`'9'`.
isOctDigit :: Char -> Bool
Selects ASCII octal digits, i.e. `'0'`..`'7'`.
isHexDigit :: Char -> Bool
Selects ASCII hexadecimal digits, i.e. `'0'`..`'9'`, `'a'`..`'f'`, `'A'`..`'F'`.
isLetter :: Char -> Bool
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`.
isMark :: Char -> Bool
Selects Unicode mark characters, e.g. accents and the like, which combine with preceding letters.
isNumber :: Char -> Bool
Selects Unicode numeric characters, including digits from various scripts, Roman numerals, etc.
isPunctuation :: Char -> Bool
Selects Unicode punctuation characters, including various kinds of connectors, brackets and quotes.
isSymbol :: Char -> Bool
Selects Unicode symbol characters, including mathematical and currency symbols.
isSeparator :: Char -> Bool
Selects Unicode space and separator characters.
Subranges
isAscii :: Char -> Bool
Selects the first 128 characters of the Unicode character set, corresponding to the ASCII character set.
isLatin1 :: Char -> Bool
Selects the first 256 characters of the Unicode character set, corresponding to the ISO 8859-1 (Latin-1) character set.
isAsciiUpper :: Char -> Bool
Selects ASCII upper-case letters, i.e. characters satisfying both `isAscii` and `isUpper`.
isAsciiLower :: Char -> Bool
Selects ASCII lower-case letters, i.e. characters satisfying both `isAscii` and `isLower`.
Unicode general categories
data GeneralCategory

Unicode General Categories (column 2 of the UnicodeData table) in the order they are listed in the Unicode standard.
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
Enum GeneralCategory
Eq GeneralCategory
Ix GeneralCategory
Ord GeneralCategory
Read GeneralCategory
Show GeneralCategory

generalCategory :: Char -> GeneralCategory
The Unicode general category of the character.
Case conversion
toUpper :: Char -> Char
Convert a letter to the corresponding upper-case letter, if any. Any other character is returned unchanged.
toLower :: Char -> Char
Convert a letter to the corresponding lower-case letter, if any. Any other character is returned unchanged.
toTitle :: Char -> Char
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
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 (i.e. `'0'`..`'9'`, `'a'`..`'f'`, `'A'`..`'F'`).
intToDigit :: Int -> Char
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
The `fromEnum` method restricted to the type `Char`.
chr :: Int -> Char
The `toEnum` method restricted to the type `Char`.
String representations
showLitChar :: Char -> ShowS
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
Read a string representation of a character, using Haskell source-language escape conventions. For example:
     lexLitChar  "\\nHello"  =  [("\\n", "Hello")]
readLitChar :: ReadS Char
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")]
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