Data.Char.Unicode

isAscii :: Char -> Boolean

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

isAsciiLower :: Char -> Boolean

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

isAsciiUpper :: Char -> Boolean

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

isLatin1 :: Char -> Boolean

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

isLower :: Char -> Boolean

Selects lower-case alphabetic Unicode characters (letters).

isUpper :: Char -> Boolean

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 -> Boolean

Selects alphabetic Unicode characters (lower-case, upper-case and title-case letters, plus letters of caseless scripts and modifiers letters).

isAlphaNum :: Char -> Boolean

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.

isLetter :: Char -> Boolean

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 Data.Char.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

Basic usage:

>>> isLetter 'a'
True
>>> isLetter 'A'
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

isDigit :: Char -> Boolean

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

isOctDigit :: Char -> Boolean

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

isHexDigit :: Char -> Boolean

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

isControl :: Char -> Boolean

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

isPrint :: Char -> Boolean

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

isSpace :: Char -> Boolean

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

isSpace includes non-breaking space.

isSymbol :: Char -> Boolean

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

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 -> Boolean

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

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 @ @):

>>> isSeparator '\160'
true

isPunctuation :: Char -> Boolean

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])http://www.unicode.org/reports/tr44/tr44-14.html#GC_Values_Table) part of the Unicode standard. The same document defines what is and is not a "Punctuation".

Examples

Basic usage:

>>> isPunctuation 'a'
false
>>> isPunctuation '7'
false
>>> isPunctuation '♥'
false
>>> isPunctuation '"'
true
>>> isPunctuation '?'
true
>>> isPunctuation '—'
true

isMark :: Char -> Boolean

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

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 -> Boolean

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

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

digitToInt :: Char -> Maybe Int

Convert a single digit Char to the corresponding Just Int if its argument satisfies isHexDigit, if it is one of 0..9, A..F, a..f. Anything else converts to Nothing

>>> import Data.Traversable

>>> traverse digitToInt ['0','1','2','3','4','5','6','7','8','9']
(Just [0,1,2,3,4,5,6,7,8,9])

>>> traverse digitToInt ['a','b','c','d','e','f']
(Just [10,11,12,13,14,15])

>>> traverse digitToInt ['A','B','C','D','E','F']
(Just [10,11,12,13,14,15])

>>> digitToInt 'G'
Nothing

toLower :: Char -> Char

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

toUpper :: Char -> Char

Convert a letter to the corresponding upper-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.

data GeneralCategory

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

Basic usage:

>>> :t OtherLetter
OtherLetter :: GeneralCategory

Eq instance:

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

Ord instance:

>>> NonSpacingMark <= MathSymbol
True

Enum instance (TODO: this is not implemented yet):

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

Show instance:

>>> show EnclosingMark
"EnclosingMark"

Bounded instance:

>>> bottom :: GeneralCategory
UppercaseLetter
>>> top :: GeneralCategory
NotAssigned

Constructors

• 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

Instances

• Show GeneralCategory
• Eq GeneralCategory
• Ord GeneralCategory
• Bounded GeneralCategory

unicodeCatToGeneralCat :: UnicodeCategory -> GeneralCategory

generalCatToInt :: GeneralCategory -> Int

generalCatToUnicodeCat :: GeneralCategory -> UnicodeCategory

generalCategory :: Char -> Maybe GeneralCategory

The Unicode general category of the character.

Examples

Basic usage:

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