Printing the contents of STL containers in a generic way
A generic Print function
A way of using STL algorithms combined with template functions as a means of printing the contents of any type of STL container (eg a
std::vector), containing any generic data type (eg int, std::string etc). typename T defines the generic data type held by the container, while typename InputIterator describes the STL container iterators passed to it:
[code language="cpp"]
template<typename T, typename InputIterator>
void Print(std::ostream& ostr,
InputIterator itbegin,
InputIterator itend,
const std::string& delimiter)
{
std::copy(itbegin,
itend,
std::ostream_iterator<T>(ostr, delimiter.c_str()));
}
[/code]
Example 1: std::set containing std::strings
This following example shows how the generic Print function can output a std::set containing std::string data types:
[code language="cpp"]
#include <iostream>
#include <algorithm>
#include <iterator>
#include <string>
#include set>
typedef std::set<std::string>::iterator iter_s;
template<typename T, typename InputIterator>
void Print(std::ostream& ostr,
InputIterator itbegin,
InputIterator itend,
const std::string& delimiter)
{
std::copy(itbegin,
itend,
std::ostream_iterator<T>(ostr, delimiter.c_str()));
}
int main()
{
std::string str[] = { "The", "cat", "in", "the", "hat" };
std::set<std::string> s( str, str + sizeof( str ) / sizeof( str[ 0 ] ) );
Print<std::string, iter_s>( std::cout, s.begin(), s.end(), "\n" );
return 0;
}
[/code]
Giving the following tokenized string output, delimited by newline characters, though not necessarily in the order they were inserted!
The cat hat in theExample 2:
std::vector containing ints
The following example shows how the same generic Print function can be used to output a std::vector containing int data types:
[code language="cpp"]
#include <iostream>
#include <algorithm>
#include <iterator>
#include <string>
#include <vector>
typedef std::vector<int>::iterator iter;
template<typename T, typename InputIterator>
void Print(std::ostream& ostr,
InputIterator itbegin,
InputIterator itend,
const std::string& delimiter)
{
std::copy(itbegin, itend,
std::ostream_iterator<T>(ostr, delimiter.c_str()));
}
int main()
{
int vals[] = { 1, 2, 3, 4 };
std::vector<int> v( vals, vals + sizeof( vals ) / sizeof( vals[ 0 ] ) );
Print<int, iter>( std::cout, v.begin(), v.end(), " " );
return 0;
}
[/code]
Which print the set of integers stored in the std::vector, separated by whitespaces:
1 2 3 4
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