C++ "return" without value

Question

What is the meaning if there is no value of return? Thanks

void run_algo() {
   ...
   project(tolabel->second);
   ...
}

void project(Projected &projected) {
    unsigned int sup = support(projected);
    if(sup < minsup) // minsup is a global variable
        return  ;
//-------------^--------->no expression here?    
    ...
}

Please read a C++ book before asking questions on StackOverflow. — Seth Carnegie, Mar 06 '12 at 12:30
@SethCarnegie but then he might come to StackOverflow to ask what book to read... — CashCow, Mar 06 '12 at 12:32
@CashCow: In which case, he'll find the answer [here](http://stackoverflow.com/questions/388242). — Mike Seymour, Mar 06 '12 at 12:55

score 15 · Accepted Answer · answered Mar 06 '12 at 12:45

15

Since the type of your function is void, when you use return, it exits the function immediately and back to the caller.

answered Mar 06 '12 at 12:45

Sango

176
3

score 8 · Answer 2 · answered Mar 06 '12 at 12:29

8

The function is declared as returning void. So there is no value returned. Using return in this function just means this function is finished.

answered Mar 06 '12 at 12:29

BoBTFish

19,167
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score 3 · Answer 3 · answered Mar 06 '12 at 12:29

3

It just exits the function immediately, returning to the caller.

answered Mar 06 '12 at 12:29

Graham Borland

60,055
21
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179

score 1 · Answer 4 · answered Mar 06 '12 at 12:30

1

It means that the execution of this function ends at this point, and it does not continue to the following lines of code.

answered Mar 06 '12 at 12:30

Ilya Kogan

21,995
15
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141

score 1 · Answer 5 · answered Mar 06 '12 at 12:30

It is used to exit from the function immediately. It resolves the necessity of an else statement in this case.

void project(Projected &projected) {
    unsigned int sup = support(projected);
    if(sup < minsup) // minsup is a global variable
        ;
    else {
        // ...
    }
}

score 1 · Answer 6 · answered Mar 06 '12 at 12:30

1

Jump out from current function without returning value.

answered Mar 06 '12 at 12:30

skywall

3,956
1
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52

score 0 · Answer 7 · answered Mar 06 '12 at 12:31

The return statement: Terminates the execution of a function and returns control to the calling function (or, in the case of the main function, transfers control back to the operating system). Execution resumes in the calling function at the point immediately following the call.

From msdn: http://msdn.microsoft.com/en-us/library/k68ktdwf%28v=vs.80%29.aspx

C++ "return" without value

7 Answers7

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