do-while loop

 

C++

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Technical Specifications

 

C++ language

 

Statements

Labels

label : statement

Expression statements

expression ;

Compound statements

{ statement... }

Selection statements

if

switch

Iteration statements

while

do-while

for

range for(C++11)

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break

continue

return

goto

Declaration statements

declaration ;

Try blocks

try compound-statement handler-sequence

Transactional memory

syncronized, atomic_commit, etc(TM TS)

 

Executes a statement repeatedly, until the value of condition becomes false. The test takes place after each iteration.

Syntax

attr(optional) do statement while ( expression ) ;

attr(C++11)	-	any number of attributes
expression	-	any expression which is contextually convertible to bool. This expression is evaluated after each iteration, and if it yields false, the loop is exited.
statement	-	any statement, typically a compound statement, which is the body of the loop

Notes

statement is always executed at least once, even if expression always yields false. If it should not execute in this case, while or for loop may be used.

If the execution of the loop needs to be terminated at some point, break statement can be used as terminating statement.

If the execution of the loop needs to be continued at the end of the loop body, continue statement can be used as shortcut.

Keywords

do, while

Example

Run this code

#include <iostream>
#include <algorithm>
#include <string>
 
int main()
{
    int j = 2;
    do { // compound statement is the loop body
        j += 2;
        std::cout << j << " ";
    } while (j < 9);
    std::cout << '\n';
    // common situation where do-while loop is used
    std::string s = "aba";
    std::sort(s.begin(), s.end());
    do std::cout << s << '\n'; // expression statement is the loop body
    while(std::next_permutation(s.begin(), s.end()));
}

Output:

4 6 8 10
aab
aba
baa

See also

C documentation for do-while