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Annex A (informative)
Grammar summary [gram]
1 This summary of C++ syntax is intended to be an aid to comprehension. It is not an exact statement of the language. In particular, the grammar described here accepts a superset of valid C++ constructs. Disambiguation rules (6.8, 7.1, 10.2) must be applied to distinguish expressions from declarations. Further, access control, ambiguity, and type rules must be used to weed out syntactically valid but meaningless constructs.
A.1 Keywords [gram.key]
1 New context-dependent keywords are introduced into a program by typedef (7.1.3), namespace (7.3.1), class (clause 9), enumeration (7.2), and template (clause 14) declarations.
typedef-name: identifier
namespace-name: original-namespace-name namespace-alias
original-namespace-name: identifier
namespace-alias: identifier
class-name: identifier
template-id enum-name:
identifier
template-name: identifier
Note that a typedef-name naming a class is also a class-name (9.1).
A.2
Lexical conventions [gram.lex]
§ A.2
1139
hex-quad:
hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
universal-character-name: \u hex-quad
\U hex-quad hex-quad
⃝c ISO/IEC N3035=10-0025
§ A.2
1140
preprocessing-token: header-name
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 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 e sign
pp-number E sign
pp-number .
identifier: identifier-nondigit
identifier identifier-nondigit identifier digit
identifier-nondigit: nondigit
universal-character-name
other implementation-defined characters
nondigit: one of abcdefghijklm nopqrstuvwxyz ABCDEFGHIJKLM NOPQRSTUVWXYZ_
digit: one of 0123456789
⃝c ISO/IEC
N3035=10-0025
§ A.2
1141
preprocessing-op-or-punc: one of
{ } [ ]
<::><%%>
new delete ? :: +-*/%ˆ&|∼
! = <
ˆ= &= |=
<= >= &&
and and_eq bitand or or_eq xor
literal: integer-literal
character-literal floating-literal string-literal boolean-literal pointer-literal user-defined-literal
> += -= *= /= %= << >> >>= <<= == != || ++ -- , ->* ->
integer-literal:
decimal-literal integer-suffixopt octal-literal integer-suffixopt hexadecimal-literal integer-suffixopt
decimal-literal: nonzero-digit
decimal-literal digit
octal-literal:
0
octal-literal octal-digit
hexadecimal-literal:
0x hexadecimal-digit
0X hexadecimal-digit hexadecimal-literal hexadecimal-digit
nonzero-digit: one of 123456789
octal-digit: one of 01234567
hexadecimal-digit: one of 0123456789
abcdef ABCDEF
integer-suffix:
unsigned-suffix long-suffixopt unsigned-suffix long-long-suffixopt long-suffix unsigned-suffixopt long-long-suffix unsigned-suffixopt
unsigned-suffix: one of uU
long-suffix: one of lL
long-long-suffix: one of ll LL
# ## ( ) %:%:%:;:... ..*
bitor compl not xor_eq
not_eq
⃝c ISO/IEC N3035=10-0025
§ A.2
1142
character-literal:
’ c-char-sequence ’
u’ c-char-sequence ’ U’ c-char-sequence ’ L’ c-char-sequence ’
c-char-sequence: c-char
c-char-sequence c-char
c-char:
any member of the 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-literal:
fractional-constant exponent-partopt floating-suffixopt digit-sequence exponent-part floating-suffixopt
fractional-constant:
digit-sequenceopt . digit-sequence digit-sequence .
exponent-part:
e signopt digit-sequence
E signopt digit-sequence sign: one of
+-
digit-sequence: digit
digit-sequence digit floating-suffix: one of
flFL
string-literal:
encoding-prefixopt " s-char-sequenceopt " encoding-prefixopt R raw-string
encoding-prefix:
u8 u U L
⃝c ISO/IEC N3035=10-0025
§ A.2
1143
s-char-sequence: s-char
s-char-sequence s-char
s-char:
any member of the source character set except
the double-quote ", backslash \, or new-line character
escape-sequence universal-character-name
raw-string:
" d-char-sequenceopt [ r-char-sequenceopt ] d-char-sequenceopt "
r-char-sequence: r-char
r-char-sequence r-char
r-char:
any member of the source character set, except
(1), a backslash \followed by a u or U, or
(2), a right square bracket ] followed by the initial d-char-sequence (which may be empty) followed by a double quote ".
universal-character-name
d-char-sequence: d-char
d-char-sequence d-char
d-char:
any member of the basic source character set except:
space, the left square bracket [, the right square bracket ], 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-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
user-defined-floating-literal:
fractional-constant exponent-partopt ud-suffix digit-sequence exponent-part ud-suffix
user-defined-string-literal: string-literal ud-suffix
user-defined-character-literal: character-literal ud-suffix
ud-suffix: identifier
⃝c ISO/IEC
A.3 Basic concepts
translation-unit: declaration-seqopt
A.4 Expressions
N3035=10-0025
[gram.basic]
[gram.expr]
§ A.4
1144
primary-expression: literal
this
( expression ) id-expression lambda-expression
id-expression: unqualified-id
qualified-id
unqualified-id: identifier
operator-function-id conversion-function-id literal-operator-id
∼ class-name template-id
qualified-id:
::opt nested-name-specifier templateopt unqualified-id :: identifier
:: operator-function-id
:: literal-operator-id
:: template-id
nested-name-specifier: type-name ::
namespace-name ::
nested-name-specifier identifier ::
nested-name-specifier templateopt simple-template-id ::
lambda-expression:
lambda-introducer lambda-declaratoropt compound-statement
lambda-introducer:
[ lambda-captureopt ]
lambda-capture: capture-default
capture-list
capture-default , capture-list
capture-default:
& =
capture-list: capture
capture-list , capture
capture: identifier
& identifier this
⃝c ISO/IEC N3035=10-0025
§ A.4
1145
lambda-declarator:
( parameter-declaration-clause ) attribute-specifieropt mutableopt
exception-specificationopt trailing-return-typeopt
postfix-expression: primary-expression
postfix-expression [ expression ] postfix-expression [ braced-init-list ] postfix-expression ( expression-listopt ) simple-type-specifier ( expression-listopt ) typename-specifier ( expression-listopt ) simple-type-specifier braced-init-list typename-specifier braced-init-list postfix-expression . templateopt id-expression postfix-expression -> templateopt id-expression postfix-expression . pseudo-destructor-name postfix-expression -> pseudo-destructor-name postfix-expression ++
postfix-expression --
dynamic_cast < type-id > ( expression ) static_cast < type-id > ( expression ) reinterpret_cast < type-id > ( expression ) const_cast < type-id > ( expression ) typeid ( expression )
typeid ( type-id )
expression-list: initializer-list
pseudo-destructor-name:
::opt nested-name-specifieropt
::opt nested-name-specifier template simple-template-id :: ∼ type-name ::opt nested-name-specifieropt ∼ type-name
unary-expression: postfix-expression
++ cast-expression
-- cast-expression unary-operator cast-expression sizeof unary-expression sizeof ( type-id )
sizeof ... ( identifier ) alignof ( type-id ) new-expression delete-expression
unary-operator: one of *&+-! ∼
new-expression:
::opt new new-placementopt new-type-id new-initializeropt ::opt new new-placementopt ( type-id ) new-initializeropt
new-placement:
( expression-list )
new-type-id:
type-specifier-seq new-declaratoropt
type-name :: ∼ type-name
⃝c ISO/IEC N3035=10-0025
§ A.4
1146
new-declarator:
ptr-operator new-declaratoropt noptr-new-declarator
noptr-new-declarator: [ expression ]
noptr-new-declarator [ constant-expression ]
new-initializer:
( expression-listopt )
braced-init-list
delete-expression:
::opt delete cast-expression ::opt delete [ ] cast-expression
cast-expression: unary-expression
( type-id ) cast-expression
pm-expression: cast-expression
pm-expression .* cast-expression pm-expression ->* cast-expression
multiplicative-expression: pm-expression
multiplicative-expression * pm-expression multiplicative-expression / pm-expression multiplicative-expression % pm-expression
additive-expression: multiplicative-expression
additive-expression additive-expression
shift-expression: additive-expression
shift-expression << shift-expression >>
relational-expression: shift-expression
relational-expression relational-expression relational-expression relational-expression
equality-expression: relational-expression
+ multiplicative-expression - multiplicative-expression
additive-expression additive-expression
equality-expression == relational-expression equality-expression != relational-expression
and-expression: equality-expression
and-expression & equality-expression
exclusive-or-expression: and-expression
exclusive-or-expression ˆ and-expression
inclusive-or-expression: exclusive-or-expression
inclusive-or-expression | exclusive-or-expression
< shift-expression > shift-expression <= shift-expression >= shift-expression
⃝c ISO/IEC
N3035=10-0025
logical-and-expression: inclusive-or-expression
logical-and-expression && inclusive-or-expression
logical-or-expression: logical-and-expression
logical-or-expression || logical-and-expression
conditional-expression: logical-or-expression
logical-or-expression ? expression : assignment-expression
assignment-expression: conditional-expression
logical-or-expression assignment-operator initializer-clause throw-expression
assignment-operator: one of
= *= /= %= += -= >>= <<= &= ˆ= |=
expression: assignment-expression
expression , assignment-expression constant-expression:
conditional-expression
A.5 Statements
[gram.stmt]
§ A.5
1147
statement: labeled-statement
attribute-specifieropt expression-statement attribute-specifieropt compound-statement attribute-specifieropt selection-statement attribute-specifieropt iteration-statement attribute-specifieropt jump-statement declaration-statement
attribute-specifieropt
labeled-statement: attribute-specifieropt
attribute-specifieropt attribute-specifieropt
expression-statement: expressionopt ;
compound-statement:
{ statement-seqopt }
statement-seq: statement
try-block
identifier : statement
case constant-expression : statement default : statement
statement-seq statement
selection-statement:
if ( condition ) statement
if ( condition ) statement else statement switch ( condition ) statement
condition: expression
type-specifier-seq attribute-specifieropt declarator = initializer-clause type-specifier-seq attribute-specifieropt declarator braced-init-list
⃝c ISO/IEC
N3035=10-0025
iteration-statement:
while ( condition ) statement
do statement while ( expression ) ;
for ( for-init-statement conditionopt ; expressionopt ) statement for ( for-range-declaration : expression ) statement
for-init-statement: expression-statement
simple-declaration for-range-declaration:
type-specifier-seq attribute-specifieropt declarator
jump-statement:
break ;
continue ;
return expressionopt ; return braced-init-list ; goto identifier ;
declaration-statement: block-declaration
A.6 Declarations
[gram.dcl]
§ A.6
1148
declaration-seq: declaration
declaration-seq declaration
declaration: block-declaration
function-definition template-declaration explicit-instantiation explicit-specialization linkage-specification namespace-definition empty-declaration attribute-declaration
block-declaration: simple-declaration
asm-definition namespace-alias-definition using-declaration using-directive static_assert-declaration alias-declaration opaque-enum-declaration
alias-declaration:
using identifier = type-id ;
simple-declaration:
attribute-specifieropt decl-specifier-seqopt attribute-specifieropt init-declarator-listopt ;
static_assert-declaration:
static_assert ( constant-expression , string-literal ) ;
empty-declaration:
;
⃝c ISO/IEC N3035=10-0025 attribute-declaration:
§ A.6
1149
attribute-specifier ;
decl-specifier: storage-class-specifier
type-specifier function-specifier friend
typedef constexpr
decl-specifier-seq:
decl-specifier-seqopt decl-specifier
storage-class-specifier:
register
static
thread_local
extern
mutable
function-specifier:
inline
virtual
explicit
typedef-name: identifier
type-specifier: trailing-type-specifier
class-specifier enum-specifier
trailing-type-specifier: simple-type-specifier
elaborated-type-specifier typename-specifier cv-qualifier
type-specifier-seq:
type-specifier type-specifier-seqopt
trailing-type-specifier-seq:
trailing-type-specifier trailing-type-specifier-seqopt
⃝c ISO/IEC N3035=10-0025
§ A.6
1150
simple-type-specifier:
::opt nested-name-specifieropt type-name
::opt nested-name-specifier template simple-template-id char
char16_t
char32_t
wchar_t
bool
short
int
long
signed
unsigned
float
double
void
auto
decltype ( expression )
type-name: class-name
enum-name typedef-name
elaborated-type-specifier:
class-key ::opt nested-name-specifieropt identifier
class-key ::opt nested-name-specifieropt templateopt simple-template-id enum ::opt nested-name-specifieropt identifier
enum-name: identifier
enum-specifier:
enum-head { enumerator-listopt } enum-head { enumerator-list , }
enum-head:
enum-key identifieropt attribute-specifieropt enum-baseopt attribute-specifieropt enum-key nested-name-specifier identifier
attribute-specifieropt enum-baseopt attribute-specifieropt opaque-enum-declaration:
enum-key identifier attribute-specifieropt enum-baseopt attribute-specifieropt ;
enum-key:
enum
enum class
enum struct
enum-base:
: type-specifier-seq
enumerator-list: enumerator-definition
enumerator-list , enumerator-definition
enumerator-definition: enumerator
enumerator = constant-expression
enumerator: identifier
⃝c ISO/IEC
N3035=10-0025
§ A.6
1151
namespace-name: original-namespace-name namespace-alias
original-namespace-name: identifier
namespace-definition: named-namespace-definition unnamed-namespace-definition
named-namespace-definition: original-namespace-definition extension-namespace-definition
original-namespace-definition:
inlineopt namespace identifier { namespace-body }
extension-namespace-definition:
inlineopt namespace original-namespace-name { namespace-body }
unnamed-namespace-definition:
inlineopt namespace { namespace-body }
namespace-body: declaration-seqopt
namespace-alias: identifier
namespace-alias-definition:
namespace identifier = qualified-namespace-specifier ;
qualified-namespace-specifier:
::opt nested-name-specifieropt namespace-name
using-declaration:
using typenameopt ::opt nested-name-specifier unqualified-id ; using :: unqualified-id ;
using-directive:
attribute-specifieropt using namespace ::opt
asm-definition:
asm ( string-literal ) ;
linkage-specification:
extern string-literal { declaration-seqopt } extern string-literal declaration
attribute-specifier:
[ [ attribute-list ] ]
attribute-list: attributeopt
attribute-list , attributeopt attribute ...
attribute-list , attribute ...
attribute:
attribute-token attribute-argument-clauseopt
attribute-token: identifier
attribute-scoped-token
attribute-scoped-token: attribute-namespace :: identifier
nested-name-specifieropt namespace-name ;
⃝c ISO/IEC attribute-namespace:
identifier attribute-argument-clause:
( balanced-token-seq )
balanced-token-seq: balanced-token
balanced-token-seq balanced-token
balanced-token:
( balanced-token-seq )
[ balanced-token-seq ]
{ balanced-token-seq }
any token other than a parenthesis, a bracket, or a brace
A.7 Declarators
N3035=10-0025
§ A.7
1152
init-declarator-list: init-declarator
init-declarator-list , init-declarator init-declarator:
declarator initializeropt
declarator: ptr-declarator
noptr-declarator parameters-and-qualifiers trailing-return-type
ptr-declarator: noptr-declarator
ptr-operator ptr-declarator
noptr-declarator:
declarator-id attribute-specifieropt
noptr-declarator parameters-and-qualifiers
noptr-declarator [ constant-expressionopt ] attribute-specifieropt ( ptr-declarator )
parameters-and-qualifiers:
( parameter-declaration-clause ) attribute-specifieropt cv-qualifier-seqopt
ref-qualifieropt exception-specificationopt
trailing-return-type:
-> attribute-specifieropt trailing-type-specifier-seq
-> attribute-specifieropt abstract-declaratoropt
ptr-operator:
* attribute-specifieropt cv-qualifier-seqopt
&
&&
::opt nested-name-specifier * attribute-specifieropt
cv-qualifier-seq:
cv-qualifier cv-qualifier-seqopt
cv-qualifier:
const
volatile
ref-qualifier:
& &&
cv-qualifier-seqopt
[gram.decl]
⃝c ISO/IEC N3035=10-0025
§ A.7
1153
declarator-id:
...opt id-expression
::opt nested-name-specifieropt class-name type-id:
type-specifier-seq attribute-specifieropt abstract-declaratoropt
abstract-declarator: ptr-abstract-declarator
noptr-abstract-declaratoropt parameters-and-qualifiers trailing-return-type ...
ptr-abstract-declarator: noptr-abstract-declarator
ptr-operator ptr-abstract-declaratoropt
noptr-abstract-declarator:
noptr-abstract-declaratoropt parameters-and-qualifiers noptr-abstract-declaratoropt [ constant-expression ] attribute-specifieropt ( ptr-abstract-declarator )
parameter-declaration-clause: parameter-declaration-listopt ...opt parameter-declaration-list , ...
parameter-declaration-list: parameter-declaration
parameter-declaration-list , parameter-declaration
parameter-declaration:
decl-specifier-seq attribute-specifieropt declarator
decl-specifier-seq attribute-specifieropt declarator = assignment-expression decl-specifier-seq attribute-specifieropt abstract-declaratoropt
decl-specifier-seq attribute-specifieropt abstract-declaratoropt = assignment-expression
function-definition:
decl-specifier-seqopt attribute-specifieropt declarator function-body decl-specifier-seqopt attribute-specifieropt declarator = default ; decl-specifier-seqopt attribute-specifieropt declarator = delete ;
function-body:
ctor-initializeropt compound-statement function-try-block
initializer: brace-or-equal-initializer
( expression-list )
brace-or-equal-initializer: = initializer-clause
braced-init-list
initializer-clause: assignment-expression
braced-init-list
initializer-list: initializer-clause ...opt
initializer-list , initializer-clause ...opt
braced-init-list:
{ initializer-list ,opt }
{}
⃝c ISO/IEC A.8 Classes
N3035=10-0025
[gram.class]
A.9
member-declarator-list , member-declarator
member-declarator:
declarator pure-specifieropt
declarator brace-or-equal-initializeropt
identifieropt attribute-specifieropt : constant-expression
pure-specifier:
=0
Derived classes
base-clause:
: base-specifier-list
base-specifier-list: base-specifier ...opt
base-specifier-list , base-specifier ...opt
base-specifier:
::opt nested-name-specifieropt class-name attribute-specifieropt
[gram.derived]
§ A.9
1154
class-name: identifier
simple-template-id class-specifier:
class-head { member-specificationopt }
class-head:
class-key identifieropt attribute-specifieropt base-clauseopt
class-key nested-name-specifier identifier attribute-specifieropt base-clauseopt
class-key nested-name-specifieropt simple-template-id attribute-specifieropt base-clauseopt
class-key:
class
struct
union
member-specification:
member-declaration member-specificationopt access-specifier : member-specificationopt
member-declaration: decl-specifier-seqopt
attribute-specifieropt member-declarator-listopt ; function-definition ;opt
::opt nested-name-specifier templateopt using-declaration static_assert-declaration template-declaration
member-declarator-list: member-declarator
unqualified-id ;
virtual access-specifieropt ::opt access-specifier virtualopt ::opt
access-specifier:
private
protected
public
nested-name-specifieropt class-name attribute-specifieropt nested-name-specifieropt class-name attribute-specifieropt
⃝c ISO/IEC
A.10 Special member functions
conversion-function-id:
operator conversion-type-id
conversion-type-id:
type-specifier-seq attribute-specifieropt conversion-declaratoropt
conversion-declarator:
ptr-operator conversion-declaratoropt
ctor-initializer:
: mem-initializer-list
mem-initializer-list: mem-initializer ...opt
mem-initializer , mem-initializer-list ...opt
mem-initializer:
mem-initializer-id ( expression-listopt ) mem-initializer-id braced-init-list
mem-initializer-id:
::opt nested-name-specifieropt class-name identifier
A.11 Overloading
operator-function-id: operator operator
N3035=10-0025
[gram.special]
operator: one of
new delete new[]
delete[] +-*/%ˆ&|∼
! = < > += -= *= /= %= ˆ= &= |= << >> >>= <<= == != <= >= && || ++ -- , ->* -> () []
literal-operator-id:
operator "" identifier
A.12 Templates
template-declaration:
exportopt template < template-parameter-list > declaration
template-parameter-list: template-parameter
template-parameter-list , template-parameter
template-parameter: type-parameter
parameter-declaration
type-parameter:
class ...opt identifieropt
class identifieropt = type-id
typename ...opt identifieropt
typename identifieropt = type-id
template < template-parameter-list > class ...opt identifieropt template < template-parameter-list > class identifieropt = id-expression
§ A.12
[gram.temp]
[gram.over]
1155
⃝c ISO/IEC simple-template-id:
template-name < template-argument-listopt >
template-id: simple-template-id
operator-function-id < template-argument-listopt > literal-operator-id < template-argument-listopt >
template-name: identifier
template-argument-list:
template-argument ...opt
template-argument-list , template-argument ...opt
template-argument: constant-expression
N3035=10-0025
type-id id-expression
typename-specifier:
typename ::opt typename ::opt
nested-name-specifier identifier nested-name-specifier templateopt
simple-template-id
explicit-instantiation:
externopt template declaration
explicit-specialization:
template < > declaration
A.13 Exception handling
try-block:
try compound-statement handler-seq
[gram.except]
function-try-block:
try ctor-initializeropt compound-statement handler-seq
handler-seq:
handler handler-seqopt
handler:
catch ( exception-declaration ) compound-statement
exception-declaration:
type-specifier-seq declarator type-specifier-seq abstract-declarator type-specifier-seq
...
throw-expression:
throw assignment-expressionopt
exception-specification
throw ( type-id-listopt )
type-id-list:
type-id ...opt
type-id-list , type-id ...opt A.14 Preprocessing directives
preprocessing-file: groupopt
§ A.14
[gram.cpp]
1156
⃝c ISO/IEC N3035=10-0025 group:
§ A.14
1157
group-part
group group-part
group-part: if-section
control-line text-line
# non-directive
if-section:
if-group elif-groupsopt else-groupopt endif-line
if-group:
# if
# ifdef
# ifndef
elif-groups: elif-group
constant-expression new-line groupopt identifier new-line groupopt
identifier new-line groupopt
elif-groups elif-group elif-group:
# elif
else-group:
# else
endif-line:
# endif
control-line:
# include
# define
# define
# define
# define
# undef
# line
# error
# pragma
# new-line
constant-expression new-line groupopt new-line groupopt
new-line
pp-tokens new-line
identifier replacement-list new-line
identifier lparen identifier-listopt ) replacement-list new-line identifier lparen ... ) replacement-list new-line
text-line:
pp-tokensopt new-line
non-directive:
pp-tokens new-line
lparen:
identifier lparen identifier-list, ... identifier new-line
pp-tokens new-line
pp-tokensopt new-line
pp-tokensopt new-line
) replacement-list new-line
a ( character not immediately preceded by white-space
identifier-list: identifier
identifier-list , identifier replacement-list:
pp-tokensopt
pp-tokens: preprocessing-token
pp-tokens preprocessing-token
⃝c ISO/IEC N3035=10-0025
§ A.14
1158
new-line:
the new-line character