/* Closest Pair Problem */
closest: procedure options (main);
   declare n fixed binary;

   get list (n);
   begin;
      declare 1 P(n),
               2 x float,
               2 y float;
      declare (i, ii, j, jj) fixed binary;
      declare (distance, min_distance initial (0) ) float;

      get list (P);
      min_distance = sqrt( (P.x(1) - P.x(2))**2 + (P.y(1) - P.y(2))**2 );
      ii = 1;  jj = 2;
      do i = 1 to n;
         do j = 1 to n;
            distance = sqrt( (P.x(i) - P.x(j))**2 + (P.y(i) - P.y(j))**2 );
            if distance > 0 then
             if distance < min_distance  then
               do;
                  min_distance = distance;
                  ii = i; jj = j;
               end;
         end;
      end;
      put skip edit ('The minimum distance ', min_distance,
                     ' is between the points [', P.x(ii),
                     ',', P.y(ii), '] and [', P.x(jj), ',', P.y(jj), ']' )
                     (a, f(6,2));
   end;
end closest;