problem2 mod

gistfile1.hrl

grid_id(Lat, Long, XMax, YMax) ->
	{X, Y} = scale(Long, Lat, XMax, YMax),
	grid_id(X, Y, XMax div 2, YMax div 2, []).
		
grid_id(_, _, X, Y, Val) when (X < 1) andalso (Y < 1)-> 
  list_to_integer(lists:reverse(Val));
grid_id(X, Y, XTh, YTh, Val) when (X > XTh) andalso (Y > YTh) ->
	grid_id(X - XTh, Y - YTh, XTh div 2, YTh div 2, [$4|Val]);
grid_id(X, Y, XTh, YTh, Val) when (X > XTh) andalso (Y =< YTh) ->
	grid_id(X - XTh, Y, XTh div 2, YTh div 2, [$3|Val]);
grid_id(X, Y, XTh, YTh, Val) when (X =< XTh) andalso (Y > YTh) ->
	grid_id(X, Y - YTh, XTh div 2, YTh div 2, [$2|Val]);
grid_id(X, Y, XTh, YTh, Val) ->
	grid_id(X, Y, XTh div 2, YTh div 2, [$1|Val]).
	
scale(X, Y, XMax, YMax) ->
	{((X + 180.0) / 360.0) * XMax, ((Y + 90.0) / 180.0) * YMax}.