fold is generally meaning "iterate over". There are no true loops in Erlang. Most all of that is done either via recursion or accessor functions (which probably are implemented recursively).
Look at lists:fold( ) and try that first. wings_vertex:fold will behave like that.
If you are very serious about learning Erlang/Wings3D programming ... I would be willing to do a few Q.A. study up sessions with you to help get you going. But there is no replacement for some talent plus the drive to dive in head first. Good luck.
Another way of putting it ... wings_vertex:fold and some of the other fold function help to keep you at arms length and protect you from the details of W.E.D.S. that Micheus points to ... nevertheless ... that sort of background WEDS information is good for you.
Look at lists:fold( ) and try that first. wings_vertex:fold will behave like that.
If you are very serious about learning Erlang/Wings3D programming ... I would be willing to do a few Q.A. study up sessions with you to help get you going. But there is no replacement for some talent plus the drive to dive in head first. Good luck.
Another way of putting it ... wings_vertex:fold and some of the other fold function help to keep you at arms length and protect you from the details of W.E.D.S. that Micheus points to ... nevertheless ... that sort of background WEDS information is good for you.