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).

A String is a list of characters. String constants in Haskell are values of type String.

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

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

Selects lower-case alphabetic Unicode characters (letters).

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.

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.

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.

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

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

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

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

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:

• UppercaseLetter
• LowercaseLetter
• TitlecaseLetter
• ModifierLetter
• OtherLetter

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

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

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

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:

• NonSpacingMark
• SpacingCombiningMark
• EnclosingMark

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

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

>>> map isMark "ò"
[False,True]

>>> isMark '✓'
False

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:

• DecimalNumber
• LetterNumber
• OtherNumber

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

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

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

>>> isNumber 'Ⅸ'
True

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:

• ConnectorPunctuation
• DashPunctuation
• OpenPunctuation
• ClosePunctuation
• InitialQuote
• FinalQuote
• OtherPunctuation

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

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

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:

• MathSymbol
• CurrencySymbol
• ModifierSymbol
• OtherSymbol

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

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

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

Selects Unicode space and separator characters.

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

• Space
• LineSeparator
• ParagraphSeparator

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

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

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

>>> isSeparator '\160'
True

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

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

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

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

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

>>> :t OtherLetter
OtherLetter :: GeneralCategory

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

>>> NonSpacingMark <= MathSymbol
True

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

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

>>> show EnclosingMark
"EnclosingMark"

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

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

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

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

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

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

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.

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

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

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

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

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.

The fromEnum method restricted to the type Char.

The toEnum method restricted to the type Char.

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

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

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

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

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")]