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Return vs return functions?

To return or not to return, this is a question for functions! Or, does it really matter?

Here is the story : I used to write code as follows:

Type3 myFunc(Type1 input1, Type2 input2){}

But recently, my project colleges told me that I should try as little as possible to avoid writing such a function, and suggest the next way by putting the return value in the input parameters.

void myFunc(Type1 input1, Type2 input2, Type3 &output){}

They convinced me that it’s better and faster due to the extra copy step when returning in the first method.

For me, I am beginning to believe that the second way is better in some situations, especially I have a few things that need to be returned or changed. For example: the second line of the next will be better and faster than the first, which avoids copying everything vecor<int>when you return.

vector<int> addTwoVectors(vector<int> a, vector<int> b){}
void addTwoVectors(vector<int> a, vector<int> b, vector<int> &result){}:

But in some other situations I can’t buy it. For example,

bool checkInArray(int value, vector<int> arr){}

will definitely be better than

void checkInArray(int value, vector<int> arr, bool &inOrNot){}

In this case, I think the first method directly returning the result is better in terms of better readability.

So, I'm confused (focused on C ++):

  • What should be returned by functions and what should not (or try to avoid)?
  • Is there any standard way or good suggestions for me?
  • Can we work better in both readability and code efficiency?

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XCode MacBook. return:

    xorl    %eax, %eax
    .align  4, 0x90
LBB0_1:                                 ## =>This Inner Loop Header: Depth=1
    leal    (%rsi,%rax), %ecx
    movl    %ecx, (%rdi,%rax,4)
    incq    %rax
    cmpl    $10000, %eax            ## imm = 0x2710
    jne     LBB0_1
## BB#2:
    movq    %rdi, %rax
    popq    %rbp
    ret

:

    xorl    %eax, %eax
    .align  4, 0x90
LBB1_1:                                 ## =>This Inner Loop Header: Depth=1
    leal    (%rdi,%rax), %ecx
    movl    %ecx, (%rdx,%rax,4)
    incq    %rax
    cmpl    $10000, %eax            ## imm = 0x2710
    jne     LBB1_1
## BB#2:
    popq    %rbp
    ret

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