Reference lets a function to return a variable . But strange things happen :(:(

[karthikbalaguru]

Hi,

I wonder how the 'm' value is 10 in the program below . It should be
7.
Further, it turns later to 11. Strange. How is it possible ? Why ?
Need clarification. Any ideas ?

using namespace std;
#include <iostream>
double &biggest (double &r, double &s)
{
if (r > s) return r;
else
return s;
}

int main ()
{
double k = 3;
double m = 7;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 7
cout << endl;
biggest (k, m) = 10;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 10 /* How is this
possible . m was actually 7. how it prints 10 */
cout << endl;
biggest (k, m) ++;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 11 /* How is it 11
here */
cout << endl;
return 0;
}

Any ideas ?

Thx in advans,
Karthik Balaguru

 

[=?ISO-8859-1?Q?Erik_Wikstr=F6m?=]

Hi,

I wonder how the 'm' value is 10 in the program below . It should be
7.
Further, it turns later to 11. Strange. How is it possible ? Why ?
Need clarification. Any ideas ?

using namespace std;
#include <iostream>
double &biggest (double &r, double &s)
{
if (r > s) return r;
else
return s;
}

int main ()
{
double k = 3;
double m = 7;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 7
cout << endl;
biggest (k, m) = 10;

This sets the value of m to 10, what did you think the '=' meant?

cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 10 /* How is this
possible . m was actually 7. how it prints 10 */
cout << endl;
biggest (k, m) ++;

Here you increase the value of m by one, what else did you expect the
'++' to do?

cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 11 /* How is it 11
here */
cout << endl;
return 0;
}

Any ideas ?

Read up on references, you clearly have not understood what they are.

 

[Alf P. Steinbach]

* karthikbalaguru:

[posting HOMEWORK]

Please see the FAQ about posting homework.

I wonder how the 'm' value is 10 in the program below . It should be
7.
Further, it turns later to 11. Strange. How is it possible ? Why ?
Need clarification. Any ideas ?

using namespace std;
#include <iostream>
double &biggest (double &r, double &s)
{
if (r > s) return r;
else
return s;
}

int main ()
{
double k = 3;
double m = 7;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 7
cout << endl;
biggest (k, m) = 10;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 10 /* How is this
possible . m was actually 7. how it prints 10 */
cout << endl;
biggest (k, m) ++;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 11 /* How is it 11
here */
cout << endl;
return 0;
}

Any ideas ?

Yes, see the FAQ item about posting HOMEWORK.

 

[karthikbalaguru]

Hi,

I wonder how the 'm' value is 10 in the program below . It should be
7.
Further, it turns later to 11. Strange. How is it possible ? Why ?
Need clarification. Any ideas ?

using namespace std;
#include <iostream>
double &biggest (double &r, double &s)
{
if (r > s) return r;
else
return s;
}

int main ()
{
double k = 3;
double m = 7;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 7
cout << endl;
biggest (k, m) = 10;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 10 /* How is this
possible . m was actually 7. how it prints 10 */
cout << endl;
biggest (k, m) ++;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 11 /* How is it 11
here */
cout << endl;
return 0;
}

Any ideas ?

Thx in advans,
Karthik Balaguru

Hey, I got it correct now.
biggest(k,m) returns m as &m which is an alias for m and so m gets
modified to 10 .
and the same thing happens with biggest(k,m)++ and so the m gets
incremented to 11.

Thx,
Karthik Balaguru

 

[karthikbalaguru]

This sets the value of m to 10, what did you think the '=' meant?


Here you increase the value of m by one, what else did you expect the
'++' to do?


Read up on references, you clearly have not understood what they are.

Apologies, there was some misunderstanding.
I did not look into it properly.

Karthik Balaguru

 

[Barry]

Hi,

I wonder how the 'm' value is 10 in the program below . It should be
7.
Further, it turns later to 11. Strange. How is it possible ? Why ?
Need clarification. Any ideas ?

using namespace std;
#include <iostream>
double &biggest (double &r, double &s)
{
if (r > s) return r;
else
return s;
}

int main ()
{
double k = 3;
double m = 7;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 7
cout << endl;
biggest (k, m) = 10;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 10 /* How is this
possible . m was actually 7. how it prints 10 */

10 is right, what else you expect?

cout << endl;
biggest (k, m) ++;
cout << "k: " << k << endl; // Displays 3
cout << "m: " << m << endl; // Displays 11 /* How is it 11
here */

11 is right too.

cout << endl;
return 0;
}

Any ideas ?

biggest() always return a reference to m, as m is always bigger than k
changes made to the returned reference (m), will directly affect referee
m. which is a reference do.

see cout you use
cout << ".." << ".." is also the case,

which is changing your buffer in the output stream that cout references

 

[terminator]

Here you increase the value of m by one, what else did you expect the
'++' to do?

hey,incing a double???
I used to think that '++' operates on integral types.Were I
wrong ?????

thanks,
FM.

 

[=?ISO-8859-1?Q?Erik_Wikstr=F6m?=]

hey,incing a double???
I used to think that '++' operates on integral types.Were I
wrong ?????

It can be used on any arithmetic (integral or floating-point) type.

 

[BobR]

Here you increase the value of m by one, what else did you expect the
'++' to do?

/* """
hey,incing a double???
I used to think that '++' operates on integral types.Were I
wrong ?????

""" */

for( double v( 1.0 ); v <= 3; ++v ){
std::cout<<"v = "<< v <<std::endl;
} // for(v)
/* - output -
v = 1.000000
v = 2.000000
v = 3.000000
*/

I was surprised it worked when I tried it.

 

[Jack Klein]

It can be used on any arithmetic (integral or floating-point) type.

Actually it can be used to any arithmetic type or pointers to any
completely defined types.

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://c-faq.com/
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.learn.c-c++
http://www.club.cc.cmu.edu/~ajo/docs/FAQ-acllc.html

 

[terminator]

Actually it can be used to any arithmetic type or pointers to any
completely defined types.

pointers look much like integrals indeed.but double/float was news to
me.

thanks every 1,
FM