C++: A Dialog Programming with the C++ Standard Library

The const Modifier for Reference Arguments

As you may recall from our discussion of types of arguments in earlier chapters, when you call a function using a value argument, the argument that you supply in the calling function isn't the one that the called function receives. Instead, a copy is made of the calling function's argument, and the called function works on the copy. While this is fine most of the time, in this case it won't work properly for reasons that will be apparent shortly; instead, we have to use a reference argument. As we saw in the discussion of reference arguments in Chapter 6, such an argument is not a copy of the caller's argument, but another name for the actual argument provided by the caller. This has a number of consequences. ...