Ulam spiral, take 2

Mostly this is posted for its pleasantly recursive nature. In response to many people asking me how I made the Ulam Spiral, I have produced a a PDF of the spiral which includes the code to make said PDF. I really like how it turned out.

One subtle touch that fellow Python programmers will appreciate is that every column begins with a line of code that is not indented.

Published 7 May 2010

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http://www.mostlymaths.net/ Ruben Berenguel

Nice! As a PostScript (somewhat) junkie, I'd love to see a PostScript program to draw it. But this is just part of my geeky nature, after writing a Mandelbrot drawer and a few L-systems (koch's island and Gosper's snowflake) and stars (line generated) for a Christmas postcard two years ago. Maybe I'll think of it when I am in a postscripting mood.

Ruben
http://home.manhattan.edu/~peter.boothe/ Peter Boothe

To do it right, you would really want to make your program a quine – http://en.wikipedia.org/wiki/Quine_(computing) – and to draw the Ulam spiral up top and then print out its own source code below. I wussed out and made my program read its source code through file I/O and I feel slightly bad about that.
http://canonical.org/~kragen/ Kragen Javier Sitaker

This is awesome! Thanks for sharing! I wonder if there's something more interesting than random.random() to use to color the dots?

I wrote a program to do this a little while ago, although I didn't really know Python yet, so I used Perl: http://lists.canonical.org/pipermail/kragen-hac…. I didn't know what it was called yet, though.

I guess it's a little hard to extract the code from that page, so I just uploaded it to http://canonical.org/~kragen/sw/spiral-ps and the output (converted to PDF, because it's smaller and more widely supported) to http://canonical.org/~kragen/sw/ulam-spiral.pdf.

Ruben: as you can see from that code, already more of it is done in PostScript than in Perl; the Perl part just does the Sieve of Eratosthenes, which would be straightforward to do in PS too. The program is in the public domain, like everything posted to kragen-hacks without a notice to the contrary.
http://home.manhattan.edu/~peter.boothe/ Peter Boothe

Many people have asked that, and the answer is, I think, that there are *way too many* options for how to color the dots. It turns out that there are lots of kinds of primes: twin primes, mersenne primes, fermat primes, etc etc etc – http://en.wikipedia.org/wiki/List_of_prime_numbers – lists more than 82 kinds! I could, I suppose, download all of those lists and devise a coloring scheme. But the random color idea served me for a good start. The code can be either scraped from the PDF, or an earlier version of the code can be found linked from http://imprompt.us/2010/ulam-spiral-algorithm/ . I encourage you to make your own!
http://zoomicon.wordpress.com/2011/07/08/prime-links/ Prime links « George Birbilis @zoomicon

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Ulam spiral, take 2

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