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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. Disam- biguation 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 con- structs.
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
hex-quad:
hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
universal-character-name: \u hex-quad
\U hex-quad hex-quad
[gram.lex]
A−2 Grammar summary
DRAFT: 7 February 2004
A.2 Lexical conventions
preprocessing-token: header-name
identifier
pp-number
character-literal
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:
h-char-sequence h-char
any member of the source character set except new-line and >
q-char-sequence: q-char
q-char:
q-char-sequence q-char
any member of the source character set except new-line and "
pp-number: digit
. digit
pp-number digit pp-number nondigit pp-number e sign pp-number E sign pp-number .
identifier:
nondigit
identifier nondigit identifier digit
nondigit: one of universal-character-name
_abcdefghijklm nopqrstuvwxyz ABCDEFGHIJKLM NOPQRSTUVWXYZ
digit: one of 0123456789
A.2 Lexical conventions DRAFT: 7 February 2004 Grammar summary A−3
preprocessing-op-or-punc: one of
{ } [ ] # ## ( )
<: :> <% %> %: %:%: ; : ... new delete? :: . .* +-*/%ˆ&| ̃ ! = < > += -= *= /= %= ˆ= &= |= << >> >>= <<= == != <= >= && || ++ -- , ->* -> and and_eq bitand bitor compl not not_eq
or or_eq xor xor_eq
literal:
integer-literal character-literal floating-literal string-literal boolean-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
long-suffix unsigned-suffixopt unsigned-suffix: one of
uU
long-suffix: one of lL
A−4 Grammar summary
DRAFT: 7 February 2004
A.2 Lexical conventions
character-literal: ’c-char-sequence’
L’c-char-sequence’
c-char-sequence: c-char
c-char:
c-char-sequence 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: "s-char-sequenceopt"
L"s-char-sequenceopt"
A.2 Lexical conventions DRAFT: 7 February 2004
Grammar summary A−5
s-char-sequence: s-char
s-char:
s-char-sequence s-char
any member of the source character set except
the double-quote ", backslash \, or new-line character
escape-sequence universal-character-name
boolean-literal:
false true
A.3 Basic concepts
translation-unit: declaration-seqopt
A.4 Expressions
primary-expression: literal
this
( expression ) id-expression
id-expression: unqualified-id
qualified-id
unqualified-id: identifier
operator-function-id conversion-function-id ̃ class-name template-id
qualified-id:
::opt nested-name-specifier templateopt unqualified-id :: identifier
:: operator-function-id
:: template-id
nested-name-specifier:
class-or-namespace-name :: nested-name-specifieropt class-or-namespace-name :: template nested-name-specifier
class-or-namespace-name: class-name
namespace-name
[gram.basic]
[gram.expr]
A−6 Grammar summary DRAFT: 7 February 2004 A.4 Expressions
postfix-expression: primary-expression
postfix-expression [ expression ]
postfix-expression ( expression-listopt )
simple-type-specifier ( expression-listopt )
typename ::opt nested-name-specifier identifier ( expression-listopt )
typename ::opt nested-name-specifier templateopt template-id ( expression-listopt ) 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: assignment-expression
expression-list , assignment-expression
pseudo-destructor-name:
::opt nested-name-specifieropt type-name :: ̃ type-name
::opt nested-name-specifier template 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 ) 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
new-declarator:
ptr-operator new-declaratoropt
direct-new-declarator
direct-new-declarator:
[ expression ]
direct-new-declarator [ constant-expression ]
A.4 Expressions DRAFT: 7 February 2004 Grammar summary A−7
new-initializer:
( expression-listopt )
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 + multiplicative-expression additive-expression - multiplicative-expression
shift-expression: additive-expression
shift-expression << additive-expression shift-expression >> additive-expression
relational-expression: shift-expression
relational-expression relational-expression relational-expression relational-expression
equality-expression: relational-expression
< shift-expression > shift-expression <= shift-expression >= shift-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
logical-and-expression: inclusive-or-expression
logical-and-expression && inclusive-or-expression
A−8 Grammar summary DRAFT: 7 February 2004
A.4 Expressions
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 assignment-expression throw-expression
assignment-operator: one of
= *= /= %= += -= >>= <<= &= ˆ= |=
expression: assignment-expression
expression , assignment-expression constant-expression:
conditional-expression
A.5 Statements
statement:
labeled-statement expression-statement compound-statement selection-statement iteration-statement jump-statement declaration-statement try-block
labeled-statement:
identifier : statement
case constant-expression : statement default : statement
expression-statement: expressionopt ;
compound-statement:
{ statement-seqopt }
statement-seq: statement
statement-seq statement
selection-statement:
if ( condition ) statement
if ( condition ) statement else statement switch ( condition ) statement
condition:
expression
type-specifier-seq declarator = assignment-expression
[gram.stmt.stmt]
A.5 Statements DRAFT: 7 February 2004
Grammar summary A−9
iteration-statement:
while ( condition ) statement
do statement while ( expression ) ;
for ( for-init-statement conditionopt ; expressionopt ) statement
for-init-statement: expression-statement
simple-declaration
jump-statement:
break ;
continue ;
return expressionopt ; goto identifier ;
declaration-statement: block-declaration
A.6 Declarations
declaration-seq: declaration
declaration-seq declaration
declaration: block-declaration
function-definition template-declaration explicit-instantiation explicit-specialization linkage-specification namespace-definition
block-declaration: simple-declaration
asm-definition namespace-alias-definition using-declaration using-directive
simple-declaration:
decl-specifier-seqopt init-declarator-listopt ;
decl-specifier: storage-class-specifier
type-specifier function-specifier friend typedef
decl-specifier-seq:
decl-specifier-seqopt decl-specifier
storage-class-specifier:
auto
register
static
extern
mutable
[gram.dcl.dcl]
A−10 Grammar summary
DRAFT: 7 February 2004
A.6 Declarations
function-specifier:
inline
virtual
explicit
typedef-name: identifier
type-specifier: simple-type-specifier
class-specifier enum-specifier elaborated-type-specifier cv-qualifier
simple-type-specifier:
::opt nested-name-specifieropt type-name
::opt nested-name-specifier template template-id char
wchar_t
bool
short
int
long
signed
unsigned
float
double
void
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 template-id enum::opt nested-name-specifieropt identifier
typename ::opt nested-name-specifier identifier
typename ::opt nested-name-specifier templateopt template-id
enum-name: identifier
enum-specifier:
enum identifieropt { enumerator-listopt }
enumerator-list: enumerator-definition
enumerator-list , enumerator-definition
enumerator-definition: enumerator
enumerator = constant-expression
enumerator: identifier
A.6 Declarations
DRAFT: 7 February 2004
Grammar summary A−11
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:
namespace identifier{ namespace-body }
extension-namespace-definition:
namespace original-namespace-name { namespace-body }
unnamed-namespace-definition:
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:
using namespace ::opt nested-name-specifieropt namespace-name ;
asm-definition:
asm ( string-literal ) ;
linkage-specification:
extern string-literal { declaration-seqopt } extern string-literal declaration
A.7 Declarators
init-declarator-list: init-declarator
init-declarator-list , init-declarator
init-declarator:
declarator initializeropt
[gram.dcl.decl]
A−12 Grammar summary
DRAFT: 7 February 2004
A.7 Declarators
declarator:
direct-declarator
ptr-operator declarator
direct-declarator: declarator-id
direct-declarator ( parameter-declaration-clause ) cv-qualifier-seqopt exception-specificationopt direct-declarator [ constant-expressionopt ]
( declarator )
ptr-operator:
* cv-qualifier-seqopt
&
::opt nested-name-specifier * cv-qualifier-seqopt
cv-qualifier-seq:
cv-qualifier cv-qualifier-seqopt
cv-qualifier:
const
volatile
declarator-id: id-expression
type-id:
::opt nested-name-specifieropt type-name type-specifier-seq abstract-declaratoropt
type-specifier-seq:
type-specifier type-specifier-seqopt
abstract-declarator:
ptr-operator abstract-declaratoropt
direct-abstract-declarator
direct-abstract-declarator: direct-abstract-declaratoropt
( parameter-declaration-clause ) cv-qualifier-seqopt exception-specificationopt direct-abstract-declaratoropt [ constant-expressionopt ]
( 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 declarator
decl-specifier-seq declarator = assignment-expression decl-specifier-seq abstract-declaratoropt
decl-specifier-seq abstract-declaratoropt = assignment-expression
A.7 Declarators DRAFT: 7 February 2004
Grammar summary A−13
function-definition:
decl-specifier-seqopt declarator ctor-initializeropt function-body decl-specifier-seqopt declarator function-try-block
function-body: compound-statement
initializer:
= initializer-clause
(expression-list )
initializer-clause: assignment-expression
{ initializer-list ,opt } {}
initializer-list: initializer-clause
initializer-list , initializer-clause
A.8 Classes
class-name: identifier
template-id class-specifier:
class-head { member-specificationopt } class-head:
[gram.class]
class-key identifieropt base-clauseopt
class-key nested-name-specifier identifier base-clauseopt class-key nested-name-specifieropt template-id base-clauseopt
class
struct
union
member-specification:
member-declaration member-specificationopt
access-specifier : member-specificationopt
member-declaration:
decl-specifier-seqopt member-declarator-listopt ; function-definition ;opt
::opt nested-name-specifier templateopt unqualified-id ; using-declaration
template-declaration
member-declarator-list: member-declarator
member-declarator-list , member-declarator
member-declarator:
declarator pure-specifieropt
declarator constant-initializeropt identifieropt : constant-expression
class-key:
A−14 Grammar summary
DRAFT: 7 February 2004
A.8 Classes
pure-specifier:
=0
constant-initializer:
= constant-expression
A.9 Derived classes
base-clause:
: base-specifier-list
base-specifier-list: base-specifier
base-specifier-list , base-specifier
base-specifier:
::opt nested-name-specifieropt class-name
virtual access-specifieropt ::opt nested-name-specifieropt class-name access-specifier virtualopt ::opt nested-name-specifieropt class-name
access-specifier:
private
protected
public
A.10 Special member functions
conversion-function-id:
operator conversion-type-id
conversion-type-id:
type-specifier-seq conversion-declaratoropt
conversion-declarator:
ptr-operator conversion-declaratoropt
ctor-initializer:
: mem-initializer-list
mem-initializer-list: mem-initializer
mem-initializer , mem-initializer-list mem-initializer:
mem-initializer-id ( expression-listopt )
mem-initializer-id:
::opt nested-name-specifieropt class-name
identifier
A.11 Overloading
operator-function-id:
operator operator
operator operator < template-argument-listopt >
[gram.class.derived]
[gram.special]
[gram.over]
A.11 Overloading DRAFT: 7 February 2004
Grammar summary A−15
operator:
one of
new delete new[] delete[] +-*/%ˆ&| ̃ ! = < > +=-=*=/=%= ˆ= &= |= << >> >>=<<=== != <= >= && || ++ -- , ->* -> () []
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 identifieropt
classidentifieropt = type-id
typename identifieropt
typenameidentifieropt = type-id
template < template-parameter-list > class identifieropt
template < template-parameter-list > class identifieropt = id-expression
template-id:
template-name < template-argument-listopt >
template-name: identifier
template-argument-list: template-argument
template-argument-list , template-argument
template-argument: assignment-expression
type-id id-expression
explicit-instantiation:
template declaration
explicit-specialization:
template < > declaration
A.13 Exception handling
try-block:
try compound-statement handler-seq function-try-block:
try ctor-initializeropt function-body handler-seq handler handler-seqopt
[gram.temp]
handler-seq:
[gram.except]
A−16 Grammar summary DRAFT: 7 February 2004
A.13 Exception handling
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
type-id-list , type-id A.14 Preprocessing directives
preprocessing-file: groupopt
group:
group-part
group group-part
group-part:
pp-tokensopt new-line
if-section control-line
if-group elif-groupsopt else-groupopt endif-line
#if constant-expression new-line groupopt #ifdef identifier new-line groupopt
# ifndef identifier new-line groupopt
[gram.cpp]
if-section:
if-group:
elif-groups: elif-group
elif-groups elif-group elif-group:
#elif constant-expression new-line groupopt else-group:
endif-line:
#else new-line groupopt # endif new-line
A.14 Preprocessing directives DRAFT: 7 February 2004 Grammar summary A−17
control-line:
lparen:
# include #define # define #undef #line
# error
# pragma
#
pp-tokens new-line
identifier replacement-list new-line
identifier lparen identifier-listopt ) replacement-list new-line identifier new-line
pp-tokens new-line
pp-tokensopt new-line
pp-tokensopt new-line
new-line
the left-parenthesis character without preceding white-space
replacement-list: pp-tokensopt
pp-tokens:
preprocessing-token
new-line:
pp-tokens preprocessing-token
the new-line character