Which is more efficient: Return a value vs. Pass by reference?

Question

I am currently studying how to write efficient C++ code, and on the matter of function calls, a question comes to mind. Comparing this pseudocode function:

n         


        

Answer 1

This pseudocode function:

not-void function-name () {
    do-something
    return value;
}

would be better used when the returned value does not require any further modifications onto it. The parameter passed is only modified in the function-name. There are no more references required to it.

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otherwise-identical pseudocode function:

void function-name (not-void& arg) {
    do-something
    arg = value;
}

would be useful if we have another method moderating the value of the same variable like and we need to keep the changes made to the variable by either of the call.

void another-function-name (not-void& arg) {
    do-something
    arg = value;
}