When to use references as parameters in C++

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What's the difference between passing by reference vs. passing by value?

If I have a function that takes in some parameters and then does something with the parameters without needing to change their inherent value, is there any benefit from using pass by reference versus pass by value?

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Yes. Passing by value copies the argument, which might be very expensive (or not even possible). If you want to pass by reference, but not modify the object, pass by const -reference.

As an example of an object that cannot be passed by value:

class Foo {
public:
    Foo() {}
private:
    Foo(const Foo&); // copy-constructor is not accessible
}

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Here is the general guide:

Pass by reference when

You need to cause a side effect on the object that will be visible to the caller

or you cannot pass by value because of the lack of an accessible copy constructor or something and you need side effects

Pass by const reference when you have

A large object

and/or you cannot pass by value

and/or no need for side effects

Pass by value when

The object is small

and/or You do not need side effects

and/or You need a copy of the value to work with anyway

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