How can I copy some range of element from a vector<string> to a string without an explicit loop?

[Fred]

Hi:
I've got the following request: (suppose the required head file
is included)

vector<string> vec;
// ..........
// push some items into vec

string str; // here I want to
copy some range of elements from vec to str, for example, from vec[2]
to vec[5]

copy( vec.begin()+2, vec.begin()+5,
str.begin() ); // Fail

string temp( vec.begin()+2,
vec.begin()+5 ); // Construct a temporary string containing vec[2] to
vec[5] and then copy temp to str, fail again

So, is there anyway that without starting an explicit loop but
achieve my goal? Thanks for help!

 

[Gianni Mariani]

Hi:
I've got the following request: (suppose the required head file
is included)

vector<string> vec;

You mean :

std::vector<char> vec;

Right ?

std::string( &vec[2], &vec[5]+1 );

Should work.

// ..........
// push some items into vec

string str; // here I want to
copy some range of elements from vec to str, for example, from vec[2]
to vec[5]

copy( vec.begin()+2, vec.begin()+5,
str.begin() ); // Fail

string temp( vec.begin()+2,
vec.begin()+5 ); // Construct a temporary string containing vec[2] to
vec[5] and then copy temp to str, fail again

So, is there anyway that without starting an explicit loop but
achieve my goal? Thanks for help!

 

[Fred]

You mean :

std::vector<char> vec;

Right ?

std::string( &vec[2], &vec[5]+1 );

Should work.

Agree.

Thanks for answering, but my problem remains unresolved.

// ..........
// push some items into vec

string str; // here I want to
copy some range of elements from vec to str, for example, from vec[2]
to vec[5]

copy( vec.begin()+2, vec.begin()+5,
str.begin() ); // Fail

string temp( vec.begin()+2,
vec.begin()+5 ); // Construct a temporary string containing vec[2] to
vec[5] and then copy temp to str, fail again

So, is there anyway that without starting an explicit loop but
achieve my goal? Thanks for help!- Hide quoted text -

- Show quoted text -

 

[Kishore Yada]

Hi:
I've got the following request: (suppose the required head file
is included)

vector<string> vec;
// ..........
// push some items into vec

string str; // here I want to
copy some range of elements from vec to str, for example, from vec[2]
to vec[5]

copy( vec.begin()+2, vec.begin()+5,
str.begin() ); // Fail

string temp( vec.begin()+2,
vec.begin()+5 ); // Construct a temporary string containing vec[2] to
vec[5] and then copy temp to str, fail again

So, is there anyway that without starting an explicit loop but
achieve my goal? Thanks for help!

I think accumulate should work.

str = accumulate( vec.begin()+2, vec.begin()+5, string() );

I could not test if the above code compiles as I do not have a C++
compiler with me at present.

 

[Alan Johnson]

You mean :

std::vector<char> vec;

Right ?

std::string( &vec[2], &vec[5]+1 );

Should work.

Agree.

Thanks for answering, but my problem remains unresolved.

// ..........
// push some items into vec
string str; // here I want to
copy some range of elements from vec to str, for example, from vec[2]
to vec[5]
copy( vec.begin()+2, vec.begin()+5,
str.begin() ); // Fail
string temp( vec.begin()+2,
vec.begin()+5 ); // Construct a temporary string containing vec[2] to
vec[5] and then copy temp to str, fail again
So, is there anyway that without starting an explicit loop but
achieve my goal? Thanks for help!- Hide quoted text -

- Show quoted text -

It's hard to tell exactly what behavior you want. Is this it, maybe?

#include <string>
#include <sstream>
#include <iterator>
#include <algorithm>
#include <vector>
#include <iostream>

using namespace std ;

int main()
{
vector<string> strings ;
strings.push_back("String0") ;
strings.push_back("String1") ;
strings.push_back("String2") ;
strings.push_back("String3") ;
strings.push_back("String4") ;
strings.push_back("String5") ;
strings.push_back("String6") ;

stringstream ss ;
copy(strings.begin() + 2, strings.begin() + 6,
ostream_iterator<string>(ss, " ")) ;

cout << ss.str() << endl ;
}

 

[peter koch]

Hi:
I've got the following request: (suppose the required head file
is included)

vector<string> vec;
// ..........
// push some items into vec

string str; // here I want to
copy some range of elements from vec to str, for example, from vec[2]
to vec[5]

copy( vec.begin()+2, vec.begin()+5,
str.begin() ); // Fail

string temp( vec.begin()+2,
vec.begin()+5 ); // Construct a temporary string containing vec[2] to
vec[5] and then copy temp to str, fail again

So, is there anyway that without starting an explicit loop but
achieve my goal? Thanks for help!

My approach would be to use a stringstream. Something like:

std::vector<std::string> vec;
std::stringstream ss;
std:stream_iterator<std::string> s(ss," ");
std::string str;
...
std::copy(vec.begin() + 2,vec.begin() +
5,std:stream_iterator<std::string>(ss," "));
std::string str = ss.str();

The advantage is that this allows a separator between the elements (if
so desired) and that you can use any type of vector so long as its
elements are streamable. You could create a (templated) function to
simplify use.
Kishore Yadas idea is also nice. It is simpler but restricted to
containers of strings.

/Peter