Re: compile error about auto_ptr

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"George" <George@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:878AA930-A216-4BE1-8B32-BDACF5E6EFB9@xxxxxxxxxxxxx
`auto_ptr' may be copied and see "vc.push_back (pi);" statement.
The signature of `vector::push_back' method requires const
parameter. But `auto_ptr' doesn't provide such constructor. That's

Sorry, Alex. I do not agree that the error comes from the push_back
method input. There is no problem to pass non-const reference to
const reference, but not vice versa (this is the root cause of this
issue).

To prove it, here is my code. Any comment?

class Foo
{
};

class myVector{
public:
void push_back (const Foo& input)
{
}
void foo()
{
Foo f;
push_back (f);
}
};

To make this resemble the situation with vector and auto_ptr, do two
things.

a) Add a Foo copy-constructor that takes Foo& (thus suppressing an
implicitly defined one that takes const Foo&):

class Foo {
public:
Foo(Foo&) {}
};

b) In push_back, actually make a copy of the parameter, as
vector::push_back has to do:

void push_back (const Foo& input) {
Foo copy = input;
}

See if you get an error now.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925


.

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