Re: [Haskell-cafe] Powerset of a set

This was one of the most woundrous moments I ever had with reading a Haskell library: If lists are used to represent finite sets (hence disregarding order and multiplicity of elements), then Control.Monad.filterM (const [False,True]) :: [a] -> [[a]] computes the powerset. Exercise for Jorge: Read the source code of filterM [*], understand what this function is doing, and why this indeed computes (a representation of) the powerset. Cheers, Olaf [*] http://hackage.haskell.org/package/base-4.8.1.0/docs/src/Control.Monad.html#...