Is there a way to use a std::ostream_iterator (or similar) such that the delimiter isn't placed for the last element?
#include <iterator>
#include <vector>
#include <algorithm>
#include <string>
using namespace std;
int main(int argc, char *argv[]) {
std::vector<int> ints = {10,20,30,40,50,60,70,80,90};
std::copy(ints.begin(),ints.end(),std::ostream_iterator<int>(std::cout, ","));
}
Will print
10,20,30,40,50,60,70,80,90,
I'm trying to avoid the trailing the delimiter. I want to print
10,20,30,40,50,60,70,80,90
Sure, you could use a loop:
for(auto it = ints.begin(); it != ints.end(); it++){
std::cout << *it;
if((it + 1) != ints.end()){
std::cout << ",";
}
}
But given C++11 range based loops this is cumbersome to track position.
int count = ints.size();
for(const auto& i : ints){
std::cout << i;
if(--count != 0){
std::cout << ",";
}
}
I'm open to using Boost. I looked into boost::algorithm::join() but needed to make a copy of the ints to strings so it was a two-liner.
std::vector<std::string> strs;
boost::copy(ints | boost::adaptors::transformed([](const int&i){return boost::lexical_cast<std::string>(i);}),std::back_inserter(strs));
std::cout << boost::algorithm::join(strs,",");
Ideally I'd just like to use a std::algorithm and not have the delimiter on the last item in the range.
Thanks!
@Cubbi pointed out in a comment that is is exactly what infix_iterator does
// infix_iterator.h
//
// Lifted from Jerry Coffin's 's prefix_ostream_iterator
#if !defined(INFIX_ITERATOR_H_)
#define INFIX_ITERATOR_H_
#include <ostream>
#include <iterator>
template <class T,
class charT=char,
class traits=std::char_traits<charT> >
class infix_ostream_iterator :
public std::iterator<std::output_iterator_tag,void,void,void,void>
{
std::basic_ostream<charT,traits> *os;
charT const* delimiter;
bool first_elem;
public:
typedef charT char_type;
typedef traits traits_type;
typedef std::basic_ostream<charT,traits> ostream_type;
infix_ostream_iterator(ostream_type& s)
: os(&s),delimiter(0), first_elem(true)
{}
infix_ostream_iterator(ostream_type& s, charT const *d)
: os(&s),delimiter(d), first_elem(true)
{}
infix_ostream_iterator<T,charT,traits>& operator=(T const &item)
{
// Here's the only real change from ostream_iterator:
// Normally, the '*os << item;' would come before the 'if'.
if (!first_elem && delimiter != 0)
*os << delimiter;
*os << item;
first_elem = false;
return *this;
}
infix_ostream_iterator<T,charT,traits> &operator*() {
return *this;
}
infix_ostream_iterator<T,charT,traits> &operator++() {
return *this;
}
infix_ostream_iterator<T,charT,traits> &operator++(int) {
return *this;
}
};
#endif
#include <vector>
#include <algorithm>
#include <string>
#include <iostream>
using namespace std;
int main(int argc, char *argv[]) {
std::vector<int> ints = {10,20,30,40,50,60,70,80,90};
std::copy(ints.begin(),ints.end(),infix_ostream_iterator<int>(std::cout,","));
}
Prints:
10,20,30,40,50,60,70,80,90