Compressed powerset

ghci.hs

import Control.Monad
import Data.List
let unRoll = join .map (uncurry $ flip replicate)
let roll = map $ map (\l@(x:_) -> (x, length l)) . group:: [String] -> [[(Char, Int)]]
let powerSet = roll . nub . filterM (const [True, False]) . unRoll

powerSet [('a',2), ('b',2)]

masBonito.hs

import Control.Monad
import Data.List

powerSet = roll . nub . filterM (const [True, False]) . unRoll

unRoll = join .map (uncurry $ flip replicate)

roll :: [String] -> [[(Char, Int)]] -- monom. rest.
roll = map $ map (\l@(x:_) -> (x, length l)) . group

> powerSet [('a',2), ('b',2)]
[[('a',2),('b',2)],[('a',2),('b',1)],[('a',2)],[('a',1),('b',2)],[('a',1),('b',1)],[('a',1)],[('b',2)],[('b',1)],[]]

tocho.hs

tochoGrande = map (map (\l@(x:_) -> (x, length l)) . group) . nub . filterM (const [True, False]) . join .map (uncurry $ flip replicate)


> tochoGrande [('a',2), ('b',2)]
[[('a',2),('b',2)],[('a',2),('b',1)],[('a',2)],[('a',1),('b',2)],[('a',1),('b',1)],[('a',1)],[('b',2)],[('b',1)],[]]