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[lex.charset]

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  ## Character sets <a id="lex.charset">[[lex.charset]]</a>
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- The *basic source character set* consists of 96 characters: the space
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- character, the control characters representing horizontal tab, vertical
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- tab, form feed, and new-line, plus the following 91 graphical
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- characters:[^4]
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-
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- ``` cpp
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- a b c d e f g h i j k l m n o p q r s t u v w x y z
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- A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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- 0 1 2 3 4 5 6 7 8 9
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- _ { } [ ] # ( ) < > % : ; . ? * + - / ^ & | ~ ! = , \" '
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- ```
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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  The *universal-character-name* construct provides a way to name other
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  characters.
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  ``` bnf
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  hex-quad:
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  hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
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  ```
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  ``` bnf
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  universal-character-name:
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  '\u' hex-quad
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  '\U' hex-quad hex-quad
 
 
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  ```
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- A *universal-character-name* designates the character in ISO/IEC 10646
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- (if any) whose code point is the hexadecimal number represented by the
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- sequence of *hexadecimal-digit*s in the *universal-character-name*. The
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- program is ill-formed if that number is not a code point or if it is a
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- surrogate code point. Noncharacter code points and reserved code points
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- are considered to designate separate characters distinct from any
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- ISO/IEC 10646 character. If a *universal-character-name* outside the
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- *c-char-sequence*, *s-char-sequence*, or *r-char-sequence* of a
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- *character-literal* or *string-literal* (in either case, including
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- within a *user-defined-literal*) corresponds to a control character or
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- to a character in the basic source character set, the program is
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- ill-formed.[^5]
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-
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- [*Note 1*: ISO/IEC 10646 code points are integers in the range
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- [0, 10FFFF] (hexadecimal). A surrogate code point is a value in the
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- range [D800, DFFF] (hexadecimal). A control character is a character
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- whose code point is in either of the ranges [0, 1F] or [7F, 9F]
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- (hexadecimal). — *end note*]
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-
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- The *basic execution character set* and the *basic execution
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- wide-character set* shall each contain all the members of the basic
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- source character set, plus control characters representing alert,
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- backspace, and carriage return, plus a *null character* (respectively,
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- *null wide character*), whose value is 0. For each basic execution
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- character set, the values of the members shall be non-negative and
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- distinct from one another. In both the source and execution basic
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- character sets, the value of each character after `0` in the above list
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- of decimal digits shall be one greater than the value of the previous.
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- The *execution character set* and the *execution wide-character set* are
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- *implementation-defined* supersets of the basic execution character set
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- and the basic execution wide-character set, respectively. The values of
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- the members of the execution character sets and the sets of additional
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- members are locale-specific.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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  ## Character sets <a id="lex.charset">[[lex.charset]]</a>
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+ The *translation character set* consists of the following elements:
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+
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+ - each abstract character assigned a code point in the Unicode
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+ codespace, and
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+ - a distinct character for each Unicode scalar value not assigned to an
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+ abstract character.
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+
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+ [*Note 1*: Unicode code points are integers in the range [0, 10FFFF]
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+ (hexadecimal). A surrogate code point is a value in the range
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+ [D800, DFFF] (hexadecimal). A Unicode scalar value is any code point
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+ that is not a surrogate code point. — *end note*]
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+
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+ The *basic character set* is a subset of the translation character set,
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+ consisting of 96 characters as specified in [[lex.charset.basic]].
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+
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+ [*Note 2*: Unicode short names are given only as a means to identifying
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+ the character; the numerical value has no other meaning in this
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+ context. — *end note*]
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+
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+ **Table: Basic character set** <a id="lex.charset.basic">[lex.charset.basic]</a>
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+
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+ | character | | glyph |
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+ | -------------------- | --------------------------- | --------------------------- |
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+ | `U+0009` | character tabulation | |
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+ | `U+000b` | line tabulation | |
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+ | `U+000c` | form feed | |
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+ | `U+0020` | space | |
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+ | `U+000a` | line feed | new-line |
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+ | `U+0021` | exclamation mark | `!` |
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+ | `U+0022` | quotation mark | `"` |
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+ | `U+0023` | number sign | `#` |
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+ | `U+0025` | percent sign | `%` |
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+ | `U+0026` | ampersand | `&` |
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+ | `U+0027` | apostrophe | `'` |
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+ | `U+0028` | left parenthesis | `(` |
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+ | `U+0029` | right parenthesis | `)` |
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+ | `U+002a` | asterisk | `*` |
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+ | `U+002b` | plus sign | `+` |
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+ | `U+002c` | comma | `,` |
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+ | `U+002d` | hyphen-minus | `-` |
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+ | `U+002e` | full stop | `.` |
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+ | `U+002f` | solidus | `/` |
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+ | `U+0030` .. `U+0039` | digit zero .. nine | `0 1 2 3 4 5 6 7 8 9` |
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+ | `U+003a` | colon | `:` |
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+ | `U+003b` | semicolon | `;` |
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+ | `U+003c` | less-than sign | `<` |
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+ | `U+003d` | equals sign | `=` |
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+ | `U+003e` | greater-than sign | `>` |
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+ | `U+003f` | question mark | `?` |
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+ | `U+0041` .. `U+005a` | latin capital letter a .. z | `A B C D E F G H I J K L M` |
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+ | | | `N O P Q R S T U V W X Y Z` |
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+ | `U+005b` | left square bracket | `[` |
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+ | `U+005c` | reverse solidus | \texttt{\} |
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+ | `U+005d` | right square bracket | `]` |
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+ | `U+005e` | circumflex accent | `^` |
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+ | `U+005f` | low line | `_` |
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+ | `U+0061` .. `U+007a` | latin small letter a .. z | `a b c d e f g h i j k l m` |
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+ | | | `n o p q r s t u v w x y z` |
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+ | `U+007b` | left curly bracket | \texttt{\ |
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+ | `U+007c` | vertical line | `|` |
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+ | `U+007d` | right curly bracket | `}` |
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+ | `U+007e` | tilde | `~` |
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+
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  The *universal-character-name* construct provides a way to name other
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  characters.
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+ ``` bnf
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+ n-char: one of
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+ any member of the translation character set except the U+007d (right curly bracket) or new-line character
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+ ```
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+
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+ ``` bnf
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+ n-char-sequence:
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+ n-char
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+ n-char-sequence n-char
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+ ```
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+
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+ ``` bnf
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+ named-universal-character:
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+ '\N{' n-char-sequence '}'
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+ ```
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+
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  ``` bnf
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  hex-quad:
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  hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
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  ```
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+ ``` bnf
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+ simple-hexadecimal-digit-sequence:
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+ hexadecimal-digit
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+ simple-hexadecimal-digit-sequence hexadecimal-digit
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+ ```
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+
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  ``` bnf
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  universal-character-name:
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  '\u' hex-quad
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  '\U' hex-quad hex-quad
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+ '\u{' simple-hexadecimal-digit-sequence '}'
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+ named-universal-character
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  ```
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+ A *universal-character-name* of the form `\u` *hex-quad*, `\U`
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+ *hex-quad* *hex-quad*, or `\u{simple-hexadecimal-digit-sequence}`
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+ designates the character in the translation character set whose Unicode
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+ scalar value is the hexadecimal number represented by the sequence of
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+ *hexadecimal-digit*s in the *universal-character-name*. The program is
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+ ill-formed if that number is not a Unicode scalar value.
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+
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+ A *universal-character-name* that is a *named-universal-character*
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+ designates the corresponding character in the Unicode Standard (chapter
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+ 4.8 Name) if the *n-char-sequence* is equal to its character name or to
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+ one of its character name aliases of type “control”, “correction”, or
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+ “alternate”; otherwise, the program is ill-formed.
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+
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+ [*Note 3*: These aliases are listed in the Unicode Character Database’s
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+ `NameAliases.txt`. None of these names or aliases have leading or
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+ trailing spaces. — *end note*]
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+
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+ If a *universal-character-name* outside the *c-char-sequence*,
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+ *s-char-sequence*, or *r-char-sequence* of a *character-literal* or
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+ *string-literal* (in either case, including within a
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+ *user-defined-literal*) corresponds to a control character or to a
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+ character in the basic character set, the program is ill-formed.
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+
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+ [*Note 4*: A sequence of characters resembling a
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+ *universal-character-name* in an *r-char-sequence* [[lex.string]] does
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+ not form a *universal-character-name*. — *end note*]
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+
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+ The *basic literal character set* consists of all characters of the
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+ basic character set, plus the control characters specified in
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+ [[lex.charset.literal]].
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+
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+ **Table: Additional control characters in the basic literal character set** <a id="lex.charset.literal">[lex.charset.literal]</a>
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+
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+ | | |
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+ | -------- | --------------- |
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+ | `U+0000` | null |
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+ | `U+0007` | alert |
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+ | `U+0008` | backspace |
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+ | `U+000d` | carriage return |
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+
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+
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+ A *code unit* is an integer value of character type
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+ [[basic.fundamental]]. Characters in a *character-literal* other than a
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+ multicharacter or non-encodable character literal or in a
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+ *string-literal* are encoded as a sequence of one or more code units, as
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+ determined by the *encoding-prefix* [[lex.ccon]], [[lex.string]]; this
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+ is termed the respective *literal encoding*. The
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+ *ordinary literal encoding* is the encoding applied to an ordinary
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+ character or string literal. The *wide literal encoding* is the encoding
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+ applied to a wide character or string literal.
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+
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+ A literal encoding or a locale-specific encoding of one of the execution
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+ character sets [[character.seq]] encodes each element of the basic
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+ literal character set as a single code unit with non-negative value,
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+ distinct from the code unit for any other such element.
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+
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+ [*Note 5*: A character not in the basic literal character set can be
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+ encoded with more than one code unit; the value of such a code unit can
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+ be the same as that of a code unit for an element of the basic literal
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+ character set. — *end note*]
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+
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+ The U+0000 (null) character is encoded as the value `0`. No other
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+ element of the translation character set is encoded with a code unit of
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+ value `0`. The code unit value of each decimal digit character after the
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+ digit `0` (`U+0030`) shall be one greater than the value of the
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+ previous. The ordinary and wide literal encodings are otherwise
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+ *implementation-defined*. For a UTF-8, UTF-16, or UTF-32 literal, the
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+ Unicode scalar value corresponding to each character of the translation
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+ character set is encoded as specified in the Unicode Standard for the
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+ respective Unicode encoding form.
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