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more about "generators" (math learning tool)
Posted:
Apr 19, 2013 3:24 PM


I've been a voice here for using the free and open source tool kit a lot more in math class, not because I want vocational IT topics to swarm over a defeated math corpse, but because math is alive and well in silicon and the civilization our students inherit needs fluency / literacy in this area i.e. "maths" has become this new thing as well. Or call it STEM.
Many of the new math languages come with a "chat window" where interaction with the interpreter means a kind of dialog, with one side played by "the machine" (i.e. the logic) and the other by the human, perhaps the designer of the language (e.g. Iverson of APL), or a contributor (e.g. Tim Peters to Python), or more likely as an average user of tools (like me). We have hardware tools, and we have software tools.
At the Python chat window prompt, you may define a generator, which is like a function except instead of returning and forgetting everything, it "yields", meaning you start with an object that you nudge. I like to call it the can you kick down the road, calling up pictures of Ernest Hemingway.
>>> thegen = Bernoulli( ) # start with an object... >>> next(thegen) # that you nudge... Fraction(1, 2) >>> next(thegen) # and nudge again... Fraction(1, 6) >>> next(thegen) Fraction(0, 1) >>> next(thegen) # ... like kicking a can down the road Fraction(1, 30)
Yes, there's lots more to say about Bernoulli numbers, and we wouldn't get to that just as the generator was being introduced. In a well designed learning program, you would have a long on ramp through functions first, in parallel with likeaDolciani treatment (of sets, functions, relations, composition of functions, inverse functions, in / sur / bijective), then get to generators. The first ones would be simple "gnomon like" figurate and polyhedron growth sequences, like square and triangular numbers, like cubic numbers, like cuboctahedral numbers 1, 12, 42, 92, 162...
I've been recently reminded to promote generators by my colleague Raymond Hettinger, likewise with the Python community and presenter of one of our keynotes at this year's US Pycon in Santa Clara. In the endnotes, I give a link to a blog through a faculty page that links to Raymond's talk. I also give a pointer into the Chipy mail list where generators of Bernoulli, Gregory numbers, and digits of pi are given.
The last is of murky (to me) origin and I've only personally verified it against published sources to 1000 digits.
Kirby
Endnotes:
Python Generators (Wikieducator): http://wikieducator.org/PYTHON_TUTORIALS#Generators
Recap of Pycon 2013: http://blog.oreillyschool.com/2013/04/thekirbsterreportsbackfrompycon2013notallscriptinglanguagesareequal.html
Chipy Archives: http://mail.python.org/pipermail/chicago/2013April/011003.html
re Hemingway: http://worldgame.blogspot.com/2009/11/kickingcandownroad.html (shows cuboctahedral numbers, graphic by me using free open source tools)



