It depends on what you mean by “cost”, and properties of the host system (hardware, operating system) with respect to operations. If your cost measure is memory usage, then the calculation of cost is obvious – add up the sizes of whatever is being copied. If your measure is execution speed (or “efficiency”) then the … Read more
Arguments are passed by value, unless the function signature specifies otherwise: in void foo(type arg), arg is passed by value regardless of whether type is a simple type, a pointer type or a class type, in void foo(type& arg), arg is passed by reference. In case of arrays, the value that is passed is a … Read more
I think much confusion is generated by not communicating what is meant by passed by reference. When some people say pass by reference they usually mean not the argument itself, but rather the object being referenced. Some other say that pass by reference means that the object can’t be changed in the callee. Example: struct … Read more
Whilst something like this does what you expect: void func(int *p) { *p = 1; } int a = 2; func(&a); // a is now 1 this does not void func(int *p) { p = new int; } int *p = NULL; func(p); // p is still NULL In both cases, the function works with … Read more
Java always passes arguments by value, NOT by reference. In your example, you are still passing obj by its value, not the reference itself. Inside your method changeName, you are assigning another (local) reference, obj, to the same object you passed it as an argument. Once you modify that reference, you are modifying the original … Read more
There are questions that already deal with the difference between passing by reference and passing by value. In essence, passing an argument by value to a function means that the function will have its own copy of the argument – its value is copied. Modifying that copy will not modify the original object. However, when … Read more
You would need to use a pointer to a pointer: foo(struct node **n) To change what n points to, you do: *n = t;
I found myself disagreeing with the highest-voted answer, so I went looking for expert opinons and here they are. From http://channel9.msdn.com/Shows/Going+Deep/C-and-Beyond-2011-Scott-Andrei-and-Herb-Ask-Us-Anything Herb Sutter: “when you pass shared_ptrs, copies are expensive” Scott Meyers: “There’s nothing special about shared_ptr when it comes to whether you pass it by value, or pass it by reference. Use exactly the … Read more
I’ve read many times that making value parameters in a function const is a bad thing to do because it’s unnecessary. However, I find it occasionally helpful to me as a check that my implementation doesn’t do something I don’t intend (as in the example at the end of your question). So, while it may … Read more
There’s an extended discussion of how Java passes variables at an earlier question “Is Java pass by reference?“. Java really passes object references by value. In your code, the references for the arrays (which are objects) are passed into calculate(). These references are passed by value, which means that any changes to the values of … Read more