Re: [Haskell-cafe] Course-of-value recursion by defining a sequence as a self-referential infinite list

Your talk has been on my youtube “watch later” for awhile, finally watched it! Cheers, Vanessa McHale https://youtu.be/q8hDDTA7HmY Power series, power serious youtu.be

On Jan 20, 2025, at 8:54 AM, Douglas McIlroy wrote:

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catalanNumbers :: Num a => [a] catalanNumbers = let xs = 1 : PowerSeries.mul xs xs in xs

This example of a generating function come to life as a program deserves to be better known. Bill Burge presented it 50 years ago in "Recursive Programming Techniques", Addison-Wesley, 1975. I revisited it in "Power series, power serious", JFP 9 (1999) 323-335, where, with overloadied arithmetic, it became ts = 1 : ts^2 The technique is laid bare in ten one-liners at https://www.cs.dartmouth.edu/~doug/powser.html.

Doug _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.