Re: using STL Container across the Files

From:

Francesco <entuland@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 10 Sep 2009 04:06:10 -0700 (PDT)

Message-ID:

<86119790-8dd6-4cdf-89c1-5b5804b4d1cf@l9g2000yqi.googlegroups.com>

On Sep 10, 10:06 am, Francesco <entul...@gmail.com> wrote:

On 10 Set, 10:11, Pallav singh <singh.pal...@gmail.com> wrote:

On Aug 10, 12:59 pm, James Kanze <james.ka...@gmail.com> wrote:

On Aug 8, 8:58 pm, Pallav singh <singh.pal...@gmail.com> wrote:

On Aug 7, 12:58 pm, James Kanze <james.ka...@gmail.com> wrote:

On Aug 6, 11:18 am, Pallav singh <singh.pal...@gmail.com> wrote:

How can we use STL Contianer Across the Files
example
file1.cc
map<int,int> xyz;
file2.cc
extern map<int,int> xyz;
It gives Error.

What error? With what compiler? With the compilers I use, I
have no problems with:
file1.cc:
    #include <map>
    std::map< int, int > xyz ;
file2.cc
    #include <map>
    extern std::map< int, int > xzy ;
A bit of precaution may be necessary because of order of
initialization issues, but otherwise, there's no problem.

map1.cc
#include <iostream>
#include <map>
#include <iterator>
using namespace std;

class A
{
public :
   int x;
   int y;
void display()const
   { cout<<" Value of x " << x << endl ;
     cout<<" value of y " << y << endl ;}
};
struct compare
{
  bool operator()(const A & s1, const A & s2) const
     { return ((s1.x== s2.x) && (s1.y == s2.y)); }
};
std::map<A,int,compare> object;

This is illegal. It's undefined behavior, so it may not give
you an error, but compare is not a valid. To be valid, the
comparison function must "induce a strict weak ordering on the
values". In particular, for a comparison function comp, if we
define a function equiv( a, b ) as being ! comp( a, b ) && !
comp( b, a ), then equiv must define an equivalence
relationship; for example, equiv( a, b ) && equiv( b, c ) implies
equiv( a, c ).

object.insert(pair<A,int>(A(1,2), 2));
object.insert(pair<A,int>(A(3,4), 2));
map2.cc
#include <iostream>
#include <map>
#include <iterator>
using namespace std;
extern map<A,int,compare> object;

What's A and compare, here? I don't see any definition of them.

map<A,int,compare>::iterator iter;
int main()
{
cout << "Map size: " << object.size() << endl;
for( iter = object.begin(); iter != object.end(); ++iter=

)

cout << (*iter).first << ": " << (*iter).second=

<< endl;

return 0;
}

g++ -g map2.cc map1.cc

i am getting compilation error's

--
James Kanze (GABI Software) email:james.ka...=

@gmail.com

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++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Hi

i tried it ..........But i am getting redifnation of ostream operator

File1.cc
#include <map>
#include <iostream>
#include "File3.cc"
using namespace std;

std::map<A, int , cmp > tmp;

void func()
{
tmp.insert( pair<A , int >(A(1,1), 10) );
tmp.insert( pair<A , int >(A(2,2), 20) );
tmp.insert( pair<A , int >(A(3,3), 30) );
tmp.insert( pair<A , int >(A(4,4), 40) );
tmp.insert( pair<A , int >(A(5,5), 50) );

}

File2.cc
#include <map>
#include <iostream>
#include <iterator>
#include "File3.cc"
using namespace std;

extern std::map<A, int , cmp > tmp;
extern void func();

int main()
{
std::map< A , int ,cmp >::iterator iter;
func();

for(iter = tmp.begin(); iter != tmp.end();iter++)
{ std::cout<<(*iter).first <<" "<<(*iter).second << endl; =

}

return 0;

}

File3.cc
#include<iostream>
using namespace std;

class A
{
public :
int x;
int y;

A(int x1,int y1) // Constructor
  {
     x = x1;
     y = y1;
  }

int operator==(const A &rhs) const
   {
      if( this->x != rhs.x) return 0;
      if( this->y != rhs.y) return 0;
      return 1;
   }

friend ostream & operator<<(ostream &, const A &);

};

ostream &operator<<(ostream &output, const A &aaa)
{
output << aaa.x << ' ' << aaa.y ;
return output;

}

struct cmp
{
bool operator()(const A & lhs, const A & rhs)
{
    if(lhs.x < rhs.x ) return 1;
      return 0;
}

};

g++ File1.cc File2.cc File3.cc

i am getting redifnation of ostream operator

You have to rename "File3.cc" into something like "myheader.h", you
should include it in File1.cc and File2.cc and finally you should not
pass it directly to g++ - if I got it all right on the fly, I didn't
deeply examine it.

Don't forget about the double header inclusion checks too.

Francesco