changing reference

[winstoon]

Hi,

consider the following code...

string a = "1";
string b = "2";
string& c = a;

how do I change c to refer to b instead of a?

 

[Victor Bazarov]

consider the following code...

string a = "1";
string b = "2";
string& c = a;

how do I change c to refer to b instead of a?

There is no legal C++ way.

V

 

[Kai-Uwe Bux]

consider the following code...

string a = "1";
string b = "2";
string& c = a;

how do I change c to refer to b instead of a?

There is no "how": you cannot reseat a reference.


Best

Kai-Uwe Bux

 

[Peter]

Hi,

consider the following code...

string a = "1";
string b = "2";
string& c = a;

how do I change c to refer to b instead of a?

When a reference is initialized, it remains bound to that object as
long as the reference exists. There is no way to rebind a reference to
a different object.

 

[BobR]

Hi,
consider the following code...
string a = "1";
string b = "2";
string& c = a;
how do I change c to refer to b instead of a?

Can't reseat 'c'.

{
std::string a = "1";
std::string b = "2";
std::string &c( a );
std::cout<<"string &c(a) c="<<c<<std::endl;
a.swap( b );
std::cout<<"a.swap(b) c="<<c<<std::endl;
}
// out: string &c(a) c=1
// out: a.swap(b) c=2

 

[BobR]

{
std::string a = "1";
std::string b = "2";
std::string &c( a );
std::cout<<"string &c(a) c="<<c<<std::endl;
a.swap( b );
std::cout<<"a.swap(b) c="<<c<<std::endl;
}
// out: string &c(a) c=1
// out: a.swap(b) c=2

or, scope it:

{
std::string a = "1";
std::string b = "2";
{
std::string &c( a );
std::cout<<"string &c(a) c="<<c<<std::endl;
}
{
std::string &c( b );
std::cout<<"string &c(b) c="<<c<<std::endl;
}
}
// out: string &c(a) c=1
// out: string &c(b) c=2

 

[Sarath]

Hi,

consider the following code...

string a = "1";
string b = "2";
string& c = a;

how do I change c to refer to b instead of a?

It's not possible to change the reference. Reference is not a pointer
to the object. It's simply the same object. Something we can call
alias. So assignment after initializing reference is something like
you assign a value to the object it is referring.

See
http://www.parashift.com/c++-faq-lite/references.html#faq-8.2

Regards,
Sarath
http://sarathc.wordpress.com/

 

[sun1991]

You can not, use pointer instead.

 

[Guest]

Hi,

consider the following code...

string a = "1";
string b = "2";
string& c = a;

how do I change c to refer to b instead of a?

So called "reference" is the alias of the object it refers to. The
referer and referee have the same physical address, and the referer's
address is set at the time of initialization, it can not be changed
anyway. Consider the example below:

nt main()
{
int a = 1 ;
int b = 2;
int& c = a;

cout << "c is " << c << endl;

c = b;
cout << "Now a is:" << a << endl;

c = 3;
cout << "Now b still is:" << b << endl;

cout << "But now a is:" << a << endl;

cout << "c's address:" << &c << endl;
cout << "a's address:" << &a << endl;

return 0;
}

 

[James Kanze]

Can't reseat 'c'.

{
std::string a = "1";
std::string b = "2";
std::string &c( a );
std::cout<<"string &c(a) c="<<c<<std::endl;
a.swap( b );
std::cout<<"a.swap(b) c="<<c<<std::endl;}

// out: string &c(a) c=1
// out: a.swap(b) c=2

I'm not sure what this is supposed to show. Consider:

std::cout.setf( std::ios::boolalpha ) ;
std::string a = "1" ;
std::string b = "2" ;
std::cout << "&a = " << &a << ", &b = " << &b << std::endl ;
std::string& c = a ;
std::cout << "a = " << a
<< ", b = " << b
<< ", c = " << c
<< ", &c = " << &c << std::endl ;
a.swap( b ) ;
std::cout << "a = " << a
<< ", b = " << b
<< ", c = " << c
<< ", &c = " << &c << std::endl ;

I get:
&a = ffbedfe0, &b = ffbedfd8
a = 1, b = 2, c = 1, &c = ffbedfe0
a = 2, b = 1, c = 2, &c = ffbedfe0
You've swapped a and b, but you've not changed the binding of c
in any way. Once constructed, there is no legal way to change
the binding of a reference.

 

[terminator]

Hi,

consider the following code...

string a = "1";
string b = "2";
string& c = a;

how do I change c to refer to b instead of a?

Sorry, you can`t do that ,but I suggest using pointers instead:

string a = "a";
string b = "b";
string d = "d";
string e = "e";

string * sptr = & a;
( * sptr ) = "a is changed";

sptr = & b;
( * sptr ) = "b is changed";

( * ( sptr = & d ) ) = "d is changed";

( *( & e ) ) = "e is changed";

regards,
FM.