Say you have a list, array, vector, storage format doesn’t matter:

std::vector<int> vec; 
vec.push_back(1); 
vec.push_back(17); 
vec.push_back(9);

And you want to format this list into a comma delimited string without the trailing comma, what is the best way to do this? Example output:

1,17,9

In any language, with any list type. Post your answers here. Be sure to use code formatting for your answer, to make it easier for everyone to read.