=?ISO-8859-1?Q?Re:_What's_the_difference_between_"Type&..=AD"_with_"?=
=?ISO-8859-1?Q?const_Type&.."?=
On Dec 31 2007, 5:09 pm, Tobias <goo...@tn-home.de> wrote:
when I red the thread I've got the impression that your question
The two definitions give two of the specific types to
exclude the other two:
const Type &front() { return head->item; }
Type &front() const { return head->item; }
was not clearly answered. You are right. Both constructs
should NOT be used (assuming that head is a non-mutable member
of (*this)).
The first one is bad style. The function front() should be
const since it does not change the member and the member can
also not be changed from the caller.
The second one should even be rejected by the compiler since
returning the non-const member-reference gives the caller the
possiblility to change it (and therefore the object). Thus,
the second front function is NOT const.
The compiler only enforces shallow const. The second one
returns a reference to something pointed to, so it is fine as
far as the compiler is concerned. It is still generally bad
practice, since it allows the client code to modify the logical
value of the object through a const reference.
The usual alternatives are, of course:
Type const& front() const { return head->item ; }
Type& front() { return head->item ; }
The first allows no modification, even by the client which calls
it, and the second allows modification by the client of the
logical value of the object.
And of course, which one is called depends on the const-ness of
the object, and not on what is done with or through the return
value.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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