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A.3.2 The Package Characters.Handling

Static Semantics

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   The library package Characters.Handling has the following declaration:
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package Ada.Characters.Handling is
  pragma Preelaborate(Handling);
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--Character classification functions
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  function Is_Control           (Item : in Character) return Boolean;
  function Is_Graphic           (Item : in Character) return Boolean;
  function Is_Letter            (Item : in Character) return Boolean;
  function Is_Lower             (Item : in Character) return Boolean;
  function Is_Upper             (Item : in Character) return Boolean;
  function Is_Basic             (Item : in Character) return Boolean;
  function Is_Digit             (Item : in Character) return Boolean;
  function Is_Decimal_Digit     (Item : in Character) return Boolean
                     renames Is_Digit;
  function Is_Hexadecimal_Digit (Item : in Character) return Boolean;
  function Is_Alphanumeric      (Item : in Character) return Boolean;
  function Is_Special           (Item : in Character) return Boolean;
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--Conversion functions for Character and String
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  function To_Lower (Item : in Character) return Character;
  function To_Upper (Item : in Character) return Character;
  function To_Basic (Item : in Character) return Character;
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  function To_Lower (Item : in String) return String;
  function To_Upper (Item : in String) return String;
  function To_Basic (Item : in String) return String;
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--Classifications of and conversions between Character and ISO 646
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  subtype ISO_646 is
    Character range Character'Val(0) .. Character'Val(127);
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  function Is_ISO_646 (Item : in Character) return Boolean;
  function Is_ISO_646 (Item : in String)    return Boolean;
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  function To_ISO_646 (Item       : in Character;
                       Substitute : in ISO_646 := ' ')
    return ISO_646;
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  function To_ISO_646 (Item       : in String;
                       Substitute : in ISO_646 := ' ')
    return String;
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--Classifications of and conversions between Wide_Character and Character.
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  function Is_Character (Item : in Wide_Character) return Boolean;
  function Is_String    (Item : in Wide_String)    return Boolean;
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  function To_Character (Item       : in Wide_Character;
                         Substitute : in Character := ' ')
    return Character;
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  function To_String    (Item       : in Wide_String;
                         Substitute : in Character := ' ')
    return String;
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  function To_Wide_Character (Item : in Character) return Wide_Character;
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  function To_Wide_String    (Item : in String)    return Wide_String;
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end Ada.Characters.Handling;
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    In the description below for each function that returns a Boolean result, the effect is described in terms of the conditions under which the value True is returned. If these conditions are not met, then the function returns False.
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    Each of the following classification functions has a formal Character parameter, Item, and returns a Boolean result.
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    Is_Control
True if Item is a control character. A control character is a character whose position is in one of the ranges 0..31 or 127..159.
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    Is_Graphic
True if Item is a graphic character. A graphic character is a character whose position is in one of the ranges 32..126 or 160..255.
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    Is_Letter
True if Item is a letter. A letter is a character that is in one of the ranges 'A'..'Z' or 'a'..'z', or whose position is in one of the ranges 192..214, 216..246, or 248..255.
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    Is_Lower
True if Item is a lower-case letter. A lower-case letter is a character that is in the range 'a'..'z', or whose position is in one of the ranges 223..246 or 248..255.
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    Is_Upper
True if Item is an upper-case letter. An upper-case letter is a character that is in the range 'A'..'Z' or whose position is in one of the ranges 192..214 or 216.. 222.
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    Is_Basic
True if Item is a basic letter. A basic letter is a character that is in one of the ranges 'A'..'Z' and 'a'..'z', or that is one of the following: 'Æ', 'æ', 'Ð', 'ð', 'Þ', 'þ', or 'ß'.
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    Is_Digit
True if Item is a decimal digit. A decimal digit is a character in the range '0'..'9'.
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    Is_Decimal_Digit
A renaming of Is_Digit.
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    Is_Hexadecimal_Digit
True if Item is a hexadecimal digit. A hexadecimal digit is a character that is either a decimal digit or that is in one of the ranges 'A' .. 'F' or 'a' .. 'f'.
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    Is_Alphanumeric
True if Item is an alphanumeric character. An alphanumeric character is a character that is either a letter or a decimal digit.
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    Is_Special
True if Item is a special graphic character. A special graphic character is a graphic character that is not alphanumeric.
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    Each of the names To_Lower, To_Upper, and To_Basic refers to two functions: one that converts from Character to Character, and the other that converts from String to String. The result of each Character-to-Character function is described below, in terms of the conversion applied to Item, its formal Character parameter. The result of each String-to-String conversion is obtained by applying to each element of the function's String parameter the corresponding Character-to-Character conversion; the result is the null String if the value of the formal parameter is the null String. The lower bound of the result String is 1.
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    To_Lower
Returns the corresponding lower-case value for Item if Is_Upper(Item), and returns Item otherwise.
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    To_Upper
Returns the corresponding upper-case value for Item if Is_Lower(Item) and Item has an upper-case form, and returns Item otherwise. The lower case letters 'ß' and 'ÿ' do not have upper case forms.
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    To_Basic
Returns the letter corresponding to Item but with no diacritical mark, if Item is a letter but not a basic letter; returns Item otherwise.
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    The following set of functions test for membership in the ISO 646 character range, or convert between ISO 646 and Character.
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    Is_ISO_646
The function whose formal parameter, Item, is of type Character returns True if Item is in the subtype ISO_646.
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    Is_ISO_646
The function whose formal parameter, Item, is of type String returns True if Is_ISO_646(Item(I)) is True for each I in Item'Range.
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    To_ISO_646
The function whose first formal parameter, Item, is of type Character returns Item if Is_ISO_646(Item), and returns the Substitute ISO_646 character otherwise.
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    To_ISO_646
The function whose first formal parameter, Item, is of type String returns the String whose Range is 1..Item'Length and each of whose elements is given by To_ISO_646 of the corresponding element in Item.
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    The following set of functions test Wide_Character values for membership in Character, or convert between corresponding characters of Wide_Character and Character.
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    Is_Character
Returns True if Wide_Character'Pos(Item) <= Character'Pos(Character'Last).
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    Is_String
Returns True if Is_Character(Item(I)) is True for each I in Item'Range.
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    To_Character
Returns the Character corresponding to Item if Is_Character(Item), and returns the Substitute Character otherwise.
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    To_String
Returns the String whose range is 1..Item'Length and each of whose elements is given by To_Character of the corresponding element in Item.
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    To_Wide_Character
Returns the Wide_Character X such that Character'Pos(Item) = Wide_Character'Pos(X).
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    To_Wide_String
Returns the Wide_String whose range is 1..Item'Length and each of whose elements is given by To_Wide_Character of the corresponding element in Item.

Implementation Advice

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    If an implementation provides a localized definition of Character or Wide_Character, then the effects of the subprograms in Characters.Handling should reflect the localizations. See also 3.5.2.
NOTES
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5  A basic letter is a letter without a diacritical mark.
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6  Except for the hexadecimal digits, basic letters, and ISO_646 characters, the categories identified in the classification functions form a strict hierarchy:
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-- Control characters
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-- Graphic characters
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    -- Alphanumeric characters
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        -- Letters
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            -- Upper-case letters
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            -- Lower-case letters
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        -- Decimal digits
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    -- Special graphic characters

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