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From: coderyogi on 17 Jun 2008 05:23
The problem statement is to print the numbers from 1 to 100 and then
back to 1; without using
a) recursion
b) any loops
I've coded the solution as follows:

[CODE]

#include <iostream.h>

class list {
private:
static int count;
public:
list ()
{
cout << ++count << endl;
}
~list ()
{
cout << count-- << endl;
}
};

int main (void)
{
list a[100];
return 0;
}

[/CODE]

Although the code gives correct output with turbo c compiler, i get
following errors with g++:

/tmp/ccJCckwR.o(.list::gnu.linkonce.t.(void)+0x16): In function
`list::list(void)':
: undefined reference to `list::count'
/tmp/ccJCckwR.o(.list::gnu.linkonce.t.(void)+0x1c): In function
`list::list(void)':
: undefined reference to `list::count'
/tmp/ccJCckwR.o(.gnu.linkonce.t._._4list+0x17): In function
`list::~list(void)':: undefined reference to `list::count'
/tmp/ccJCckwR.o(.gnu.linkonce.t._._4list+0x1d): In function
`list::~list(void)':: undefined reference to `list::count'
collect2: ld returned 1 exit status

If anybody can help, thanx!

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From: d04rp on 17 Jun 2008 11:32
Correction to my last post: ignore the second solution. In order to
initialize a member within the class, the member must be cont static
and integral.

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From: Dennis on 17 Jun 2008 11:32
On Jun 17, 2:23 pm, coderyogi <zape...(a)gmail.com> wrote:
> The problem statement is to print the numbers from 1 to 100 and then
> back to 1; without using
> a) recursion
> b) any loops
> I've coded the solution as follows:
>
> [CODE]
>
> #include <iostream.h>
>
> class list {
> private:
> static int count;
> public:
> list ()
> {
> cout << ++count << endl;
> }
> ~list ()
> {
> cout << count-- << endl;
> }
>
> };
>
> int main (void)
> {
> list a[100];
> return 0;
>
> }
>
> [/CODE]
>
> Although the code gives correct output with turbo c compiler, i get
> following errors with g++:
[SNIP]

Functions can be static as declared, but to use a static member
variable, you have to declare it outside the class somewhere. Think
of it as allocating the space for your variable. I compiled your
program and it worked fine for me after putting the following line
after the class declaration:

int list::count=0;

-Dennis

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From: d04rp on 17 Jun 2008 11:31
> The problem statement is to print the numbers from 1 to 100 and then
> back to 1; without using
> a) recursion
> b) any loops
> I've coded the solution as follows:
>
> [CODE]
>
> #include <iostream.h>
>
> class list {
> private:
> static int count;
> public:
> list ()
> {
> cout << ++count << endl;
> }
> ~list ()
> {
> cout << count-- << endl;
> }
>
> };
>
> int main (void)
> {
> list a[100];
> return 0;
>
> }
>
> [/CODE]
>
> Although the code gives correct output with turbo c compiler, i get
> following errors with g++:
>
> /tmp/ccJCckwR.o(.list::gnu.linkonce.t.(void)+0x16): In function
> `list::list(void)':
> : undefined reference to `list::count'
> /tmp/ccJCckwR.o(.list::gnu.linkonce.t.(void)+0x1c): In function
> `list::list(void)':
> : undefined reference to `list::count'
> /tmp/ccJCckwR.o(.gnu.linkonce.t._._4list+0x17): In function
> `list::~list(void)':: undefined reference to `list::count'
> /tmp/ccJCckwR.o(.gnu.linkonce.t._._4list+0x1d): In function
> `list::~list(void)':: undefined reference to `list::count'
> collect2: ld returned 1 exit status
>
> If anybody can help, thanx!

You must add the following line: int list::count = 0; (e.g after the
class definition).
This is how you initialize static variables in c++. Another solution
to this problem, because count is both static and int is to initilize
it directly. ie. change static int count; to static int count = 0;

HTH Roger Schildmeijer


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From: Chris Thomasson on 17 Jun 2008 11:42
"coderyogi" <zaperaj(a)gmail.com> wrote in message
news:50d15b83-400d-4a6c-a9f8-3987adaa08ec(a)s33g2000pri.googlegroups.com...
> The problem statement is to print the numbers from 1 to 100 and then
> back to 1; without using
> a) recursion
> b) any loops
> I've coded the solution as follows:
>
> [CODE]
[...]
> [/CODE]
>
> Although the code gives correct output with turbo c compiler, i get
> following errors with g++:
[...]
>
> If anybody can help, thanx!

try this:
__________________________________________________________
#include <iostream>

class list {
static int count;

public:
list() {
std::cout << ++count << std::endl;
}

~list() {
std::cout << count-- << std::endl;
}
};

int list::count = 0;

int main() {
list a[100];
return 0;
}

__________________________________________________________




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