@AhmedG.:
Thank you for your comment. It’s always encouraging to see that people find the article useful.

“References are always “constant” (they can’t be reassigned), so const together with a reference will always make the object constant. However, this doesn’t apply to pointers:”

This needs some elaboration, i think. Only when the const appears at the type referred to, then you create a reference to const. Otherwise, your code is not valid:

int &const a = …; // not valid
int const &a = …; // correct way

However, as you say, a reference conceptually is const. A const added to a reference type using a typedef is ignored (the same applies to template parameter: this is done to simplify generic programming):

typedef int &intref_type;
intref_type const a = …;
// valid, equivalent to “int &a = …;”

Regarding whether to pass by const reference or by value, i follow the following rule:

“If the function always takes a copy, then pass by value”.

For example, in the following case, pass by value:

string toupper(string s) {
/* some code that changes s directly */
return s;
}

Passing by reference would look like the following:

string topper(string const &s) {
string tmp(s);
/* some code that changes tmp */
return tmp;
}

In general, make the function prototype as transparent to the caller as possible, which opens a good range of optimization possibilities for the caller (compiler).

I think pictures are useful when introducing pointers, but I’m not sure if a picture would help much here?

I find it helpful to think of a reference as “a different name for the same variable” and to think of pointers as “the memory address of a variable”.

I do think it’s confusing that the & and * symbols have two different meanings when used on the left and right side of an assignment. But with practice, it becomes a little easier to remember.

Something I got in my mind to write a long time ago. One thing I just tought of: would it be nice to draw some scheme of how an object with “pointer on the stack” looks like in comparison with an “object allocated at the stack” ?