How can i make a unique copy of strings?

i have problems with regards using the unique_copy stl function. it seems to not working his job right. i'm using borland, and what it does is just copy the original vector and not the unique string values. i tried to emulate it on devcpp and it produces an error..

here's the code:

Code:

#include <stdlib.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <iostream>
#include <string>

using namespace std;
  
int main()
{
 
//UNIQUE ELEMENTS

//Initialize two vectors
vector<string> v, result;
v.push_back("X");
v.push_back("X");
v.push_back("y");

//Create an insert_iterator for results
insert_iterator<vector<string>> ins(result, result.begin());

//Demonstrate includes
cout << "The vector: " << endl << "    ";
for (int i = 0; i < v.size(); i++){
    cout << v[i] << " ";
}

//Find the unique elements
unique_copy(v.begin(), v.end(), ins);

//Display the results
cout << endl << endl
     << "Has the following unique elements:"
     << endl << "     ";

//copy(result.begin(),result.end(),
for (int i = 0; i < result.size(); i++){
    cout << result[i] << " ";
}

    system("PAUSE");
    
    return 0;
}

the error is `result' cannot appear in a constant-expression and points to the insert_iterator. I'm really confused right now, if i had a vector of strings how would i get a copy with only the unique values?

example

v[0] = "X"
v[1] = "X"
v[2] = "y"

Result:

r[0] = "X"
r[1] = "y"

thanks for your help!

The space is important.

Code:

insert_iterator<vector<string> > ins(result, result.begin());

What the?! you're absolutely right! thanks!! i didn't know that the space is important. hmm... what is the space for? is is for the allocator?

now, i still have problem with borland's unique_copy but at least i'm one step one solving it

thanks again!

The compiler interprets >> as operator>> rather than two consectutive >'s.

As for Borland, I see what you see but don't have an answer.

[edit]Perhaps this?

Code:

   unique_copy(v.begin(), v.end(), 
               insert_iterator<vector<string> > (result, result.begin()));

[edit=2]As in,

Code:

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <iterator>
using namespace std;

int main()
{
   //UNIQUE ELEMENTS

   //Initialize two vectors
   vector<string> original, result;
   original.push_back("X");
   original.push_back("X");
   original.push_back("y");

   //Demonstrate includes
   cout << "original:\n";
   copy(original.begin(), original.end(), ostream_iterator<string>(cout, "\n"));

   //Find the unique elements
   unique_copy(original.begin(), original.end(), 
               insert_iterator<vector<string> > (result, result.begin()));

   //Display the results
   cout << "result:\n";
   copy(result.begin(), result.end(), ostream_iterator<string>(cout, "\n"));

   return 0;
}

/* my output
original:
X
X
y
result:
X
y
*/

i see. thank you for clearing that out. i'm actually doing a hard method of copying the vector to another then doing a unique copy for another vector. your solution is much more concise and straight forward i'll try to use that one...

the problem on borland is it does not perform a unique_copy.

Both g++ and bc55 produce the same output for me.

this is my problem:

Code:

class A {
public:
     std::string str;
    std::string& getStr(){
           return str;    
    }
}

class B{
public:
    std::vector<A> vector_A;
}

class C{
public:
   std::vector<B>vector_B;
}

int main(){
//initialize class C.
C c;
//Assuming the vectors has values...

std::vector<std::string> vstr, result;

std::vector<B>::iterator = iter_B;
std::vector<A>::iterator = iter_A;

for (iter_B = c.vector_B.begin(); iter_B < c.vector_B.end(); iter_B++){
    for ( iter_A = iter_B->vector_A.begin(); iter_A < iter_B->vector_A.end(); iter_A++){
           //place to a temporary vector        
           vstr.push_back(iter_A->getStr());
   }
}

//does not work..
 unique_copy(vstr.begin(), vstr.end(), 
               insert_iterator<vector<string> > (result, result.begin()));

   //Display the results
   cout << "result:\n";
   copy(result.begin(), result.end(), ostream_iterator<string>(cout, "\n"));

   return 0;
}

assuming all headers are included correctly...

Can you post the exact code that compiles and gives the wrong output?

The basic algorithm you are using would rely on the source vector either being sorted, or having all like strings within the source vector always being adjacent to each other. If you don't expect this to be the case, then your destination vector will end up containing duplicates.

Could you copy from your source vector into a set instead?

Code:

set<string> strset;
vector<string> strvect;

...

// Copy from vector into set, set will only contain unique elements afterwards
copy( strvect.begin(), strvect.end(), inserter(strset,strset.begin()) );

In which case the set ends up with all the unique elements from the source vector.

ok thank you for your replies.

i give up on using unique_copy and use a more borland specific method using TStringList. i guess it's not as good as using the unique_copy but at least it's working for now.