[Verba] Meeting Summary

[Stuart D. Gathman]

Last week (I'm behind on summaries), we cut up paper to model the many
ways of gluing together the edges of a screen (choices for what to do when
reaching the edge of the screen in a 2D game).  Most of the resulting 2D
surfaces can be modeled with paper, but 2, the Klein bottle and projective 
plane require 4 dimensions.  We then added a place_robot function.

This week, I went to the Chenettes, and Jilian joined via AIM.  Rebecca
and I made the place_robot function actually work, while Jilian figured
out how to CD her Windows Command prompt to the proper directory and run a
python script.  Then I played some hymns in Jazz style for Rebecca, who
very sweetly professed to like them.

Let me remind everyone that our excursions into group theory are not 
directly related to programming, but were needed to understand a problem 
domain of interest (solving Rubik's cube).  But, understanding it will 
help you excel at Math - especially abstract algebra and modern physics.

To build programming skills, you need to keep doing it - just like 
learning an instrument or sport.  Try to come up with problems to solve 
using your skills, and solve them.

Here is a simple problem related to group theory.  Remember that any group 
(including Rubik's cube) is isomorphic to a permutation group.   A basic 
operation needed for dealing with permutation groups is to list their 
members.  We introduced Python "generators" for the deal_position 
function.  This assignment asks you to create a generator that lists all 
the permutations of a sequence.  It should be written as a generator.
For instance, 

  def permute(s):
    ... blah
    blah ...
    ... yield something
    ... blah
  
print permute([1,2,3])

should output:

[1,2,3]
[1,3,2]
[2,1,3]
[2,3,1]
[3,1,2]
[3,2,1]

or the same permutations in any order.  Do not assume that the members of 
the permutation group are numbers.  They can be any Python object.

-- 
	      Stuart D. Gathman <stuart at bmsi.com>
Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flamis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.