jgrimes/weird_perms.hs

## weird_perms.hs
module Main where
import Control.Monad
import Data.List
import Data.Char (intToDigit)


perms xs n = do
  l <- replicateM n xs
  guard (length l <= n)
  let z = do x <- [0..(n - 1)]
             y <- [1..(n - 1)]
             if (x < y)
               then return (l!!x <= l!!y || l!!y == 0 || l!!y `elem` (take (y - 1) l))
               else return True
  guard (and z)
  return l

main = mapM (putStrLn . (map intToDigit)) (perms [0..9] 3)
	module Main where
	import Control.Monad
	import Data.List
	import Data.Char (intToDigit)


	perms xs n = do
	l <- replicateM n xs
	guard (length l <= n)
	let z = do x <- [0..(n - 1)]
	y <- [1..(n - 1)]
	if (x < y)
	then return (l!!x <= l!!y \|\| l!!y == 0 \|\| l!!y `elem` (take (y - 1) l))
	else return True
	guard (and z)
	return l

	main = mapM (putStrLn . (map intToDigit)) (perms [0..9] 3)