Ada Reference Manual (Ada 2022) — Legal Information

# A.3.2 The Package Characters.Handling

#### Static Semantics

1
The library package Characters.Handling has the following declaration:
2/5
with Ada.Characters.Conversions;
package Ada.Characters.Handling
with Pure is
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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;
function Is_Line_Terminator (Item : in Character) return Boolean;
function Is_Mark (Item : in Character) return Boolean;
function Is_Other_Format (Item : in Character) return Boolean;
function Is_Punctuation_Connector (Item : in Character) return Boolean;
function Is_Space (Item : in Character) return Boolean;
function Is_NFKC (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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-- The functions Is_Character, Is_String, To_Character, To_String, To_Wide_Character,
-- and To_Wide_String are obsolescent; see J.14.
Paragraphs 14 through 18 were deleted.
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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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Is_Line_Terminator
True if Item is a character with position 10 .. 13 (Line_Feed, Line_Tabulation, Form_Feed, Carriage_Return) or 133 (Next_Line).
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Is_Mark
Never True (no value of type Character has categories Mark, Non-Spacing or Mark, Spacing Combining).
32.3/3
Is_Other_Format
True if Item is a character with position 173 (Soft_Hyphen).
32.4/3
Is_Punctuation_Connector
True if Item is a character with position 95 ('_', known as Low_Line or Underscore).
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Is_Space
True if Item is a character with position 32 (' ') or 160 (No_Break_Space).
32.6/5
Is_NFKC
True if Item can be present in a string normalized to Normalization Form KC (as defined by Clause 22 of ISO/IEC 10646:2020); this includes all characters except those with positions 160, 168, 170, 175, 178, 179, 180, 181, 184, 185, 186, 188, 189, and 190.
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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.
Paragraphs 42 through 49 were deleted.
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NOTE 1 A basic letter is a letter without a diacritical mark.
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NOTE 2 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
60/3
NOTE 3 There are certain characters which are defined to be lower case letters by ISO 10646 and are therefore allowed in identifiers, but are not considered lower case letters by Ada.Characters.Handling.

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