April 12th 2008
If p is the perimeter of a right angle triangle with integral length sides, {a,b,c}, there are exactly three solutions for p = 120.
{20,48,52}, {24,45,51}, {30,40,50}
For which value of p < 1000, is the number of solutions maximised?
WARNING: CONTAINS MATHEMATICS
Continue Reading »
December 27th 2007
I am just getting a talk ready for WYLUG on python.
I sent Dave the following blurb:
Why I love Python:
A talk on the programming language Python, in 3 parts (feel free to
leave in the interludes if you have had enough)Part 1: Past, Present, Future.
A bit of history and the design of the language, a look at all the
implementations available today, quick tour of built-in and commonly
used modules and future plans.Part 2: Language overview
A quick tour of the language: builtin types, control structures, using
modules etcPart 3: Recent Magic.
Some relatively recent changes that make programming Python even more
pleasurable.
Decorators, Generators, List comprehensions, Iterators, Functools and
anything else I can fit in.
Again a whirlwind tour, but you should be impressed and want to read
up on these some more
I have been revisiting some of the Python talks I have watched over the last few years for ideas and will update my ComSci page with links.
I stumbled across some excellent video from RubyConf, particularly the Rubinius one. Rubinius is a ruby VM partially written in Ruby, taking some lessons from Python and Smalltalk. Some of the stuff he bigs up (compiling to bytecode automatically comes to mind) Python has had for ages, but the self hosting aspect is cool (not as cool as PyPy though). Rubinius seems to be doing what Avi Bryant suggested here, learn from the Smalltalk guys and the papers from the Self team that Sun spun off and later bought back to do the hotspot VM for Java. Interesting times for dynamic languages, target the JVM, CLR, self host and generate code in other languages while always writing in the same fun language. I say Ruby envy only because I think the Ruby community does a better job of looking cool and exciting people than the Python one.
Now Haskell joy. After describing working through Yet Another Haskell Tutorial to the 2 friends doing it with me as “not an obviously pleasurable experience” I had a great moment on the train the other day looking at partial application.
(\y -> y*3)
is Haskell for the anonymous function that takes y and multiplies it by 3 (I wish I had LaTeX here to draw the lamda calculus). What I like is that you can also write that as
(*3)
While this example is trivial, what is happening is interesting. The compiler knows * is an infix operator that takes 2 arguments and that is has been supplied one and “partially applies” the function, making (*3) (a function that takes one argument). One more thing is changing prefix and infix operators around using ( _ ) and ` _ ` , for example:
3 * 5
(*) 3 5
map (*2) [1,2,3]
(*2) `map` [1,2,3]
I hope this second example is clear, map usually is a prefix function that takes a function and a list and returns a list with the result of applying the function to each element (the return value here would be [2,4,6]). This flexibility is neat and is starting to make Haskell a joy to hack in.
Merry Christmas,
December 7th 2007
I gave a talk at the second python user group in leeds on Wednesday. It was called “Anatomy Of A Python Program - How Much Can You Do In 0.1 KLOC?”. It is based on Peter Norvigs Sudoku solver. I had been thinking about doing it for WYLUG, possibly as a second talk after an intro to python. The slides were the same, but instead of looking at cool features of python that make the code so concise we critiqued it a bit and spoke about the style and possible speedups. The slides for the talk is here, but as I did not add any notes, you would be better off just reading Norvigs article (though the Javascript slideshow is cool, press t to toggle views)
The slideshow was made using rst2s5 and I am amazed how well it works. Restructuredtext is from Pythons Docutils and is a simple markup language designed to be readable as plain text, see here for details. Below is part of the code for my presentation
December 1st 2007
I have been meaning for some time to tackle the RubyQuiz problems in Python.
The one from yesterday (#148) is quite interesting, taking postfix notated expressions and returning an infix version.
For example
2 3 5 + * -> 2 * (3 + 5)
I spoilt it a bit by reading Reverse Polish Notation on Wikipedia, which gave away how to evaluate the postfix expressions.
Here is my python code to evaluate postfix expressions
Continue Reading »
November 15th 2007
I posted last time about TeXmacs and remembered the plugins for using it to display output from some of the superb free maths packages (which sometimes lack a nice display).
The one I am excited about most is for SAGE. SAGE is written in python and leverages the hard work of the other projects (its motto is Building the Car Instead of Reinventing the Wheel). See the TeXmacs plugin here and some screenshots of SAGE here.
I will take a look at the code and see if I can contribute anything, it will be nice to get involved in a big project.