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

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