Return ref to a constant object

[craftindo]

Write your question here.
Using eclipse, if the object is a constant, it allows to return a constant object too. The compiler complains "invalid initialization of reference of type 'Vector&' from expression of type 'const Vector'.


But, according to book C++ Primer plus Stephen Prata page 662, it should work.

Why is that? is there any setting i need to ignore this error?

thanks



// version 1
Vector Max(const Vector & v1, const Vector & v2)
{
if (v1.magval() > v2.magval())
return v1;
else
return v2;
}

[firedraco]

In the code you posted, you aren't returning a reference, nor is the return value a constant. Did you make an error copying and pasting or something?

[craftindo]

hi Firedraco,
Thanks a lot i understand now. I made a mistake by returning a reference.

int & f1(const int & piRef) {
return piRef;
}

[firedraco]

Well, the problem there is that you are returning a non-const reference (which allows modification) to a const object (which doesn't), which you simply can't do because it violates const correctness.

If the book you are reading says you can, it is incorrect.