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

Vanessa McHale writes:

I came up with a one-liner for computing coefficients of the generating function for integer partitions:

part :: Int → [Integer ] part n = take n $ product [cycle (1 : replicate n 0) | n ← [0 . . (n − 2)]]

Karczmarczuk’s solution via the Haskell prelude:

part = 1 : b 1 where b n = (1 : b (n + 1)) + (replicate n 0 ++ b n)

This is broken code, no?, just 2 reasons I can spot why: - function 'b n' calls 'b n' unconditionally (infite loop) - What is the reutrn type of 'b'? It seems like it returns list, but the return value is in the form 'a + b' , where (+) is instance of num so I don't think prelude contains any ad-hoc definition of (+) that returns list