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Within LTS Haskell 24.46 (ghc-9.10.3)

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1. DecimalNumber :: GeneralCategory

   base	Data.Char

   Nd: Number, Decimal

2. LetterNumber :: GeneralCategory

   base	Data.Char

   Nl: Number, Letter

3. OtherNumber :: GeneralCategory

   base	Data.Char

   No: Number, Other

4. isAlphaNum :: Char -> Bool

   base	Data.Char

   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, e.g., Roman numerals like V, full-width digits like '１' (aka '65297'). This function returns True if its argument has one of the following GeneralCategorys, or False otherwise:

   • UppercaseLetter
   • LowercaseLetter
   • TitlecaseLetter
   • ModifierLetter
   • OtherLetter
   • DecimalNumber
   • LetterNumber
   • OtherNumber

5. isNumber :: Char -> Bool

   base	Data.Char

   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
   

6. module Data.Enum

   The Enum and Bounded classes.

7. class Enum a

   base	Data.Enum

   Class Enum defines operations on sequentially ordered types. The enumFrom... methods are used in Haskell's translation of arithmetic sequences. Instances of Enum may be derived for any enumeration type (types whose constructors have no fields). The nullary constructors are assumed to be numbered left-to-right by fromEnum from 0 through n-1. See Chapter 10 of the Haskell Report for more details. For any type that is an instance of class Bounded as well as Enum, the following should hold:

   • The calls succ maxBound and pred minBound should result in a runtime error.
   • fromEnum and toEnum should give a runtime error if the result value is not representable in the result type. For example, toEnum 7 :: Bool is an error.
   • enumFrom and enumFromThen should be defined with an implicit bound, thus:

   enumFrom     x   = enumFromTo     x maxBound
   enumFromThen x y = enumFromThenTo x y bound
   where
   bound | fromEnum y >= fromEnum x = maxBound
   | otherwise                = minBound
   

8. enumFrom :: Enum a => a -> [a]

   base	Data.Enum

   Used in Haskell's translation of [n..] with [n..] = enumFrom n, a possible implementation being enumFrom n = n : enumFrom (succ n).

   Examples

   • enumFrom 4 :: [Integer] = [4,5,6,7,...]

   • enumFrom 6 :: [Int] = [6,7,8,9,...,maxBound ::
     Int]

9. enumFromThen :: Enum a => a -> a -> [a]

   base	Data.Enum

   Used in Haskell's translation of [n,n'..] with [n,n'..] = enumFromThen n n', a possible implementation being enumFromThen n n' = n : n' : worker (f x) (f x n'), worker s v = v : worker s (s v), x = fromEnum n' - fromEnum n and

   f n y
   | n > 0 = f (n - 1) (succ y)
   | n < 0 = f (n + 1) (pred y)
   | otherwise = y
   
   

   Examples

   • enumFromThen 4 6 :: [Integer] = [4,6,8,10...]

   • enumFromThen 6 2 :: [Int] = [6,2,-2,-6,...,minBound ::
     Int]

10. enumFromThenTo :: Enum a => a -> a -> a -> [a]

    base	Data.Enum

    Used in Haskell's translation of [n,n'..m] with [n,n'..m] = enumFromThenTo n n' m, a possible implementation being enumFromThenTo n n' m = worker (f x) (c x) n m, x = fromEnum n' - fromEnum n, c x = bool (>=) ((x 0)

    f n y
    | n > 0 = f (n - 1) (succ y)
    | n < 0 = f (n + 1) (pred y)
    | otherwise = y
    
    

    and

    worker s c v m
    | c v m = v : worker s c (s v) m
    | otherwise = []
    
    

    Examples

    • enumFromThenTo 4 2 -6 :: [Integer] =
      [4,2,0,-2,-4,-6]

    • enumFromThenTo 6 8 2 :: [Int] = []

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