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245

answers:

2

I want to know if it is possible to transform a std::vector to a std::stringstream using generic programming and how can one accomplish such a thing?

+13  A: 

Adapting Brian Neal's comment, the following will only work if the << operator is defined for the object in the std::vector (in this example, std::string).

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

 // Dummy std::vector of strings
 std::vector<std::string> sentence;
 sentence.push_back("aa");
 sentence.push_back("ab");

 // Required std::stringstream object
 std::stringstream ss;

 // Populate
 std::copy(sentence.begin(), sentence.end(),std::ostream_iterator<std::string>(ss,"\n"));

 // Display
 std::cout<<ss.str()<<std::endl;
Jacob
+1 Yep, that's the cleanest way
David Relihan
+1 only crux is that copy and ostream_iterator should be qualified with std. :)
Skurmedel
@Skurmedel - Just saw it, thanks :)
Jacob
Would you not give the benefit of the doubt that using namespace std was at the start of the method?!!! :)
David Relihan
Lol, might as well be consistent :)
Jacob
No no no! It must *transform* the vector!
Noah Roberts
@Noah: Lol, do you propose a change of basis or a magic potion :) ?
Jacob
This fails when the vector's element type has no `operator<<`. I think the OP needs to specify the problem more.
Brian Neal
@David Relihan: I'm sure there were, but it could be confusing. :)
Skurmedel
+8  A: 

If the vector's element type supports operator<<, something like the following may be an option:

std::vector<Foo> v = ...;
std::ostringstream s;
std::copy(v.begin(), v.end(), std::ostream_iterator<Foo>(s));
Éric Malenfant