Annex A (informative) Grammar summary [gram]

hex-quad:
hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit

universal-character-name:
\u hex-quad
\U hex-quad hex-quad

preprocessing-token:
header-name
import-keyword
module-keyword
export-keyword
identifier
pp-number
character-literal
user-defined-character-literal
string-literal
user-defined-string-literal
preprocessing-op-or-punc
each non-white-space character that cannot be one of the above

token:
identifier
keyword
literal
operator-or-punctuator

header-name:
< h-char-sequence >
" q-char-sequence "

h-char-sequence:
h-char
h-char-sequence h-char

h-char:
any member of the source character set except new-line and >

q-char-sequence:
q-char
q-char-sequence q-char

q-char:
any member of the source character set except new-line and "

pp-number:
digit
. digit
pp-number digit
pp-number identifier-nondigit
pp-number ' digit
pp-number ' nondigit
pp-number e sign
pp-number E sign
pp-number p sign
pp-number P sign
pp-number .

identifier:
identifier-nondigit
identifier identifier-nondigit
identifier digit

identifier-nondigit:
nondigit
universal-character-name

nondigit: one of
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
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 _

digit: one of
0 1 2 3 4 5 6 7 8 9

keyword:
any identifier listed in Table tab:lex.key
import-keyword
module-keyword
export-keyword

preprocessing-op-or-punc:
preprocessing-operator
operator-or-punctuator

preprocessing-operator: one of
# ## %: %:%:

operator-or-punctuator: one of
{ } [ ] ( )
<: :> <% %> ; : ...
? :: . .* -> ->* ~
! + - * / % ^ & |
= += -= *= /= %= ^= &= |=
== != < > <= >= <=> && ||
<< >> <<= >>= ++ -- ,
and or xor not bitand bitor compl
and_eq or_eq xor_eq not_eq

literal:
integer-literal
character-literal
floating-point-literal
string-literal
boolean-literal
pointer-literal
user-defined-literal

integer-literal:
binary-literal integer-suffix${}_{opt}$
octal-literal integer-suffix${}_{opt}$
decimal-literal integer-suffix${}_{opt}$
hexadecimal-literal integer-suffix${}_{opt}$

binary-literal:
0b binary-digit
0B binary-digit
binary-literal '${}_{opt}$ binary-digit

octal-literal:
0
octal-literal '${}_{opt}$ octal-digit

decimal-literal:
nonzero-digit
decimal-literal '${}_{opt}$ digit

hexadecimal-literal:
hexadecimal-prefix hexadecimal-digit-sequence

binary-digit: one of
0 1

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

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

hexadecimal-prefix: one of
0x 0X

hexadecimal-digit-sequence:
hexadecimal-digit
hexadecimal-digit-sequence '${}_{opt}$ hexadecimal-digit

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${}_{opt}$
unsigned-suffix long-long-suffix${}_{opt}$
long-suffix unsigned-suffix${}_{opt}$
long-long-suffix unsigned-suffix${}_{opt}$

unsigned-suffix: one of
u U

long-suffix: one of
l L

long-long-suffix: one of
ll LL

character-literal:
encoding-prefix${}_{opt}$ ' c-char-sequence '

encoding-prefix: one of
u8  u  U  L

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

c-char:
any member of the basic source character set except the single-quote ', backslash \, or new-line character
escape-sequence
universal-character-name

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

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

octal-escape-sequence:
\ octal-digit
\ octal-digit octal-digit
\ octal-digit octal-digit octal-digit

hexadecimal-escape-sequence:
\x hexadecimal-digit
hexadecimal-escape-sequence hexadecimal-digit

floating-point-literal:
decimal-floating-point-literal
hexadecimal-floating-point-literal

decimal-floating-point-literal:
fractional-constant exponent-part${}_{opt}$ floating-point-suffix${}_{opt}$
digit-sequence exponent-part floating-point-suffix${}_{opt}$

hexadecimal-floating-point-literal:
hexadecimal-prefix hexadecimal-fractional-constant binary-exponent-part floating-point-suffix${}_{opt}$
hexadecimal-prefix hexadecimal-digit-sequence binary-exponent-part floating-point-suffix${}_{opt}$

fractional-constant:
digit-sequence${}_{opt}$ . digit-sequence
digit-sequence .

hexadecimal-fractional-constant:
hexadecimal-digit-sequence${}_{opt}$ . hexadecimal-digit-sequence
hexadecimal-digit-sequence .

exponent-part:
e sign${}_{opt}$ digit-sequence
E sign${}_{opt}$ digit-sequence

binary-exponent-part:
p sign${}_{opt}$ digit-sequence
P sign${}_{opt}$ digit-sequence

sign: one of
+ -

digit-sequence:
digit
digit-sequence '${}_{opt}$ digit

floating-point-suffix: one of
f l F L

string-literal:
encoding-prefix${}_{opt}$ " s-char-sequence${}_{opt}$ "
encoding-prefix${}_{opt}$ R raw-string

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

s-char:
any member of the basic source character set except the double-quote ", backslash \, or new-line character
escape-sequence
universal-character-name

raw-string:
" d-char-sequence${}_{opt}$ ( r-char-sequence${}_{opt}$ ) d-char-sequence${}_{opt}$ "

r-char-sequence:
r-char
r-char-sequence r-char

r-char:
any member of the source character set, except a right parenthesis ) followed by
   the initial d-char-sequence (which may be empty) followed by a double quote ".

d-char-sequence:
d-char
d-char-sequence d-char

d-char:
any member of the basic source character set except:
   space, the left parenthesis (, the right parenthesis ), the backslash \, and the control characters
   representing horizontal tab, vertical tab, form feed, and newline.

boolean-literal:
false
true

pointer-literal:
nullptr

user-defined-literal:
user-defined-integer-literal
user-defined-floating-point-literal
user-defined-string-literal
user-defined-character-literal

user-defined-integer-literal:
decimal-literal ud-suffix
octal-literal ud-suffix
hexadecimal-literal ud-suffix
binary-literal ud-suffix

user-defined-floating-point-literal:
fractional-constant exponent-part${}_{opt}$ ud-suffix
digit-sequence exponent-part ud-suffix
hexadecimal-prefix hexadecimal-fractional-constant binary-exponent-part ud-suffix
hexadecimal-prefix hexadecimal-digit-sequence binary-exponent-part ud-suffix

user-defined-string-literal:
string-literal ud-suffix

user-defined-character-literal:
character-literal ud-suffix

ud-suffix:
identifier