Const qualifiers and ampersand

Question

I'm getting confused about the const qualifier. I found and read a lot of article and similar questions such as http://www.cprogramming.com/reference/pointers/const_pointers.html.

What is not clear to me is why g++ complain about this class member:

const string& const name;

but it doesn't complain about

string& const name;

My idea is to declare a constant pointer to a constant string value. I'm using & instead of * to avoid NULL pointers.

What am I missing?

The compiler error is the following:

‘const’ qualifiers cannot be applied to ‘const string& {aka const std::__cxx11::basic_string<char>&}’
  const string& const name;
                      ^

"My idea is to declare a constant pointer..." - `&` does not declare a pointer at all. — Oliver Charlesworth, Mar 05 '16 at 14:22
Perhaps the compiler is saying "you have told me once, why the ...." — Ed Heal, Mar 05 '16 at 14:23
You are confusing references and pointers. Look them up in the index of your favorite C++ reference book. — Cody Gray - on strike, Mar 05 '16 at 14:23
@CodyGray he didn't realise he had a C++ reference book - thought it was a pointer book — M.M, Mar 05 '16 at 14:31
Downvoted because the premise of the entire question is broken. _"it doesn't complain about `string& const name;`"_ It most certainly does. — Lightness Races in Orbit, Mar 05 '16 at 15:11

score 6 · Accepted Answer · edited May 23 '17 at 12:33

6

string& const name; should fail too. References and pointers are different things.

Reference couldn't be const itself, it doesn't make sense. Unlike pointer, reference could not be bound again after initialized.

Failed demo with gcc and clang.

And see What are the differences between a pointer variable and a reference variable in C++?

edited May 23 '17 at 12:33

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answered Mar 05 '16 at 14:27

songyuanyao

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You forgot to tell him what he is missing, like the difference between pointers and references. – Cody Gray - on strike Mar 05 '16 at 14:32

Const qualifiers and ampersand

1 Answers1