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A.3.2 The Package Characters.Handling

Static Semantics

1
The library package Characters.Handling has the following declaration:

2/2

     {00362AI95−00362−01} {00395AI95−00395−01} with Ada.Characters.Conversions;
     package Ada.Characters.Handling is  pragma Pure(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;

13/2

     {00285AI95−00285−01} {00395AI95−00395−01} −− 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;

19.a/2

Discussion: {00395AI95−00395−01} The with_clause for Ada.Characters.Conversions is needed for the definition of the obsolescent functions (see J.14). It would be odd to put this clause into J.14 as it was not present in Ada 95, and with_clauses are semantically neutral to clients anyway.

20
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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{control character (a category of Character)} 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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{graphic character (a category of Character)} 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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{letter (a category of Character)} 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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{lower−case letter (a category of Character)} 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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{upper−case letter (a category of Character)} 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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{basic letter (a category of Character)} 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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{decimal digit (a category of Character)} 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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{hexadecimal digit (a category of Character)} 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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{alphanumeric character (a category of Character)} Is_Alphanumeric

True if Item is an alphanumeric character. An alphanumeric character is a character that is either a letter or a decimal digit.

32
{special graphic character (a category of Character)} Is_Special

True if Item is a special graphic character. A special graphic character is a graphic character that is not alphanumeric.

33
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.

36
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.

37
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 48 were deleted.

Implementation Advice

49/2
This paragraph was deleted.{00285AI95−00285−01}

     NOTES

50

 A basic letter is a letter without a diacritical mark.

51

 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

59.a

Ramification: Thus each Character value is either a control character or a graphic character but not both; each graphic character is either an alphanumeric or special graphic but not both; each alphanumeric is either a letter or decimal digit but not both; each letter is either upper case or lower case but not both.
Extensions to Ada 95

59.b/2

{00362AI95−00362−01} {extensions to Ada 95} Characters.Handling is now Pure, so it can be used in pure units.
Wording Changes from Ada 95

59.c/2

{00285AI95−00285−01} {00395AI95−00395−01} The conversion functions are made obsolescent; a more complete set is available in Characters.Conversions −− see A.3.4.

59.d/2

{00285AI95−00285−01} We no longer talk about localized character sets; these are a non−standard mode, which is none of our business.