Iteration over data lines in the SMINPUTS block is demonstrated in this example:
#include <fstream>
#include <iostream>
using namespace std;
using namespace SLHAea;
int main()
{
  ifstream ifs("slha1.txt");
       line != input[
"SMINPUTS"].
end(); ++line)
  {
    if (!line->is_data_line()) continue;
    cout << "index: "   << (*line)[0] << ",  "
         << "value: "   << (*line)[1] << ",  "
         << "comment: " << (*line)[2] << endl;
  }
}