species-0.1: Combinatorial species library



An interpretation of species as exponential generating functions, which count labelled structures.



labelled :: EGF -> [Integer]Source

Extract the coefficients of an exponential generating function as a list of Integers. Since EGF is an instance of Species, the idea is that labelled can be applied directly to an expression of the Species DSL. In particular, labelled s !! n is the number of labelled s-structures on an underlying set of size n. For example:

 > take 10 $ labelled octopi

gives the number of labelled octopi on 0, 1, 2, 3, ... 9 elements.