Set Containment

template <class I1, class I2>
bool g_subset_of (I1 beg1, I1 end1, I2 beg2, I2 end2)
// returns true iff range 1 is contained in range 2
{
  while (beg1 != end1 && beg2 != end2)
    if ((*beg1) < (*beg2))       // *beg1 lies below *beg2 in value_type
      return 0;
    else if ((*beg2) < (*beg1))  // *beg1 lies above *beg2 in value_type
      ++beg2;
    else                         // *beg1 == *beg2
      ++beg1, ++beg2;
  if (beg1 == end1)              // all elements of range1 have been found in range2
    return 1;
  return 0;                      // or not
}