Lego Random Hit Machine
This page is to help my godson Paul Murray (and his dad John!).
Paul (with John's help) had built and programmed a Lego mindstorm machine
which when activated, went through a series of operations, turning about its
central axis to a cardinal position, then activating an outward movement to
knock a man off his perch, then going on to the next position, for all four
positions in turn. Here are some pictures -
the machine in plan view,
the machine in side view, and
Paul with another machine he built.
Paul wanted to know how to change the program to choose positions at random
rather than in order. It took me a while to get the time to think about this,
but here is the result. I don't have a lego system myself, so I have simulated
Firstly, see a flowchart of the overall
any fairly recent Internet Explorer or Netscape).
Then look at the source code for the
then use the View pulldown menu and choose the Source option.
I intentially didn't use an array for holding the 'done' flags, even though
that would be my natural approach, and would simplify extending the simulation
to more than 4 positions. This was to keep the code simpler to understand.
Changing it to use an array and a machine with say six positions, is left as
an exercise to the reader.
Author: Paul Hardy
Last modified: 3 January 2002