8 Statements [stmt.stmt]

8.6 Iteration statements [stmt.iter]

8.6.1 General [stmt.iter.general]

Iteration statements specify looping.

iteration-statement:
while ( condition ) statement
do statement while ( expression ) ;
for ( init-statement condition

_{o p t}

_{o p t}

) statement
for ( init-statement

_{o p t}

for-range-declaration : for-range-initializer ) statement

for-range-declaration:
attribute-specifier-seq

_{o p t}

decl-specifier-seq declarator
attribute-specifier-seq

_{o p t}

decl-specifier-seq ref-qualifier

_{o p t}

[ identifier-list ]

for-range-initializer:
expr-or-braced-init-list

See [dcl.meaning] for the optional attribute-specifier-seq in a for-range-declaration.

[Note 1:

An init-statement ends with a semicolon.

— end note]

The substatement in an iteration-statement implicitly defines a block scope which is entered and exited each time through the loop.

If the substatement in an iteration-statement is a single statement and not a compound-statement, it is as if it was rewritten to be a compound-statement containing the original statement.

[Example 1:

while (--x >= 0) int i; can be equivalently rewritten as while (--x >= 0) { int i; }

Thus after the while statement, i is no longer in scope.

— end example]

If a name introduced in an init-statement or for-range-declaration is redeclared in the outermost block of the substatement, the program is ill-formed.

[Example 2: void f() { for (int i = 0; i < 10; ++i) int i = 0; // error: redeclaration for (int i : { 1, 2, 3 }) int i = 1; // error: redeclaration } — end example]