structure reference

Accelerated Computing HPC Compilers Legacy PGI Compilers
1

Hi,

I was following a book on C++ and came across the following:

According to the book this kind of code should work:

#include <iostream>
using namespace std;

struct sysop
{
    int value;
};

const sysop & use(sysop & sysopref);    // function with a reference return type

int main()
{
    sysop tester =
    {
        0
    };

    sysop & n1 = use(tester);
    cout << n1.value << endl;

    return 0;
}

// use() return the reference passed to it
const sysop & use(sysop & sysopref)
{
    sysop* psysop = new sysop;
    sysopref.value++;
    *psysop = sysopref; // copy info
    return *psysop;
}

the book says that the function is returning a reference to structure sysop, so
the type of the variable n1 in main() should be reference to structure sysop.

however I get this compiler error:

"test.cpp", line 19: error: qualifiers dropped in binding reference of type
          "sysop &" to initializer of type "const sysop"
      sysop & n1 = use(tester);
                   ^

1 error detected in the compilation of "test.cpp".

Therefore, i dropped the “&” in the assignment of n1, and then everything worked.

So now i wondered if it is a mistake in the book?
Strangely, they state that also the following code is correct:

#include <iostream>
using namespace std;

struct sysop
{
    char name[26];
    char quote[64];
    int used;
};

const sysop & use(sysop & sysopref);    // function with a reference return type

int main()
{
    sysop looper =
    {
        "Rick \"Fortran\" Looper",
        "I'm a goto kind of guy.",
        0
    };

    use(looper);                        // looper is type sysop
    cout << "Looper: " << looper.used << " use(s)\n";
    sysop copycat;
    copycat = use(looper);
    cout << "Looper: " << looper.used << " use(s)\n";
    cout << "Copycat: " << copycat.used << " use(s)\n";
    cout << "use(looper): " << use(looper).used << " use(s)\n";
    cout << "Copycat: " << copycat.used << " use(s)\n";
    return 0;
}

// use() return the reference passed to it
const sysop & use(sysop & sysopref)
{
    cout << sysopref.name << " says:\n";
    cout << sysopref.quote << endl;
    sysopref.used++;
    return sysopref;
}

Here, according to my own view, a reference to structure sysop is returned
and assigne to a structure sysop, not a reference to structure sysop.
The only difference being the fact that no pointers are used.

Also, in the first program, I wonder what kind of delete statement I should use?
I thought this would be correct:

  delete &n1

but I don’t know how to be sure.

Thanks for any insight on the intricacies of this reference stuff.

Steven