Constants

constant:
 floating-constant
 integer-constant
 character-constant
 string-literal
 enumeration-constant
 boolean-literal 

enumeration-constant:
 identifier

 floating-constant:
 fractional-constant <exponent-part> <floating-suffix>
 digit-sequence exponent-part <floating-suffix>

 character-constant:
 'c-char-sequence' (char - ANSI)
 L'c-char-sequence' (wchar_t - Widestring)
 u'c-char-sequence' (char16_t - UTF-16) (С++0x)
 U'c-char-sequence' (char32_t - UTF-32) (С++0x)

fractional-constant:
 <digit-sequence>  . digit-sequence
 digit-sequence  . 

c-char-sequence:
 c-char
 c-char-sequence c-char

exponent-part:
 e <sign> digit-sequence
 E <sign> digit-sequence

c-char:
 Any character in the source character set except
 the single-quote ( ' ), 
 backslash ( \ ),
 or newline character 
 escape-sequence

sign: one of
 + -

escape-sequence: 
 simple-escape-sequence
 octal-escape-sequence
 hexadecimal-escape-sequence

digit-sequence:
 digit
 digit-sequence digit

simple-escape-sequence: one of 
 \" \' \? \\
 \a \b \f \n \r \t \v

floating-suffix: one of
 f l F L

octal-escape-sequence:
 \ octal-digit (\o)
 \ octal-digit octal-digit (\oo)
 \ octal-digit octal-digit octal-digit (\ooo)

 integer-constant:
 decimal-constant <integer-suffix>
 octal-constant <integer-suffix>
 hexadecimal-constant <integer-suffix>

hexadecimal-escape-sequence:
 \x hexadecimal-digit (\xh)
 \X hexadecimal-digit (\Xh)
 hexadecimal-escape-sequence hexadecimal-digit

decimal-constant:
 nonzero-digit
 decimal-constant digit

 string-literal:
 "s-char-sequence" (char* - ANSI)
 L"s-char-sequence" (wchar_t* - Widestring)
 u"s-char-sequence" (char16_t* - UTF-16) (С++0x)
 U"s-char-sequence" (char32_t* - UTF-32) (С++0x)

octal-constant:
 0
 octal-constant octal-digit

s-char-sequence:
 s-char
 s-char-sequence s-char

hexadecimal-constant:
 0x hexadecimal-digit
 0X hexadecimal-digit
 hexadecimal-constant hexadecimal-digit

s-char:
 Any character in the source character set except
 the double-quote ( " ), 
 backslash ( \ ),
 or newline character 
 escape-sequence

nonzero-digit: one of
 1 2 3 4 5 6 7 8 9

 boolean-literal:
 true
 false

octal-digit: one of
 0 1 2 3 4 5 6 7

hexadecimal-digit: one of
 0 1 2 3 4 5 6 7 8 9
 a b c d e f
 A B C D E F

integer-suffix:
 unsigned-suffix <long-suffix>
 long-suffix <unsigned-suffix>
 <unsigned-suffix> size-suffix 

unsigned-suffix: one of
 u U

long-suffix: one of
 l L 

 size-suffix: one of
 i8 I8 i16 I16 i32 I32 i64 I64