Unicode.Char.Numeric

Selects Unicode character with a numeric value.

Note: a character may have a numeric value but return False with the predicate isNumber, because isNumber only tests GeneralCategory: some CJK characters are OtherLetter and do have a numeric value.

prop> isNumeric c == isJust (numericValue c)

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

Note: a character may have a numeric value (see numericValue) but return False, because isNumber only tests GeneralCategory: some CJK characters are OtherLetter and do have a numeric value. Use isNumeric to cover those cases as well.

prop> isNumber c == Data.Char.isNumber c

Numeric value of a character, if relevant.

Note: a character may have a numeric value but return False with the predicate isNumber, because isNumber only tests GeneralCategory: some CJK characters are OtherLetter and do have a numeric value.

Integer value of a character, if relevant.

This is a special case of numericValue.

Note: a character may have a numeric value but return False with the predicate isNumber, because isNumber only tests GeneralCategory: some CJK characters are OtherLetter and do have a numeric value.

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'.

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

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'

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.