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> permutate' :: (Eq a) => [a] -> Int -> [[a]]
> permutate' [] n = [[]]
> permutate' _  0 = [[]]
> permutate' xs n = [ x:ys | x <- xs, ys <- (permutate' xs (n-1))]

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languitar@Little-Tux:~/Desktop > hugs bla.lhs
__   __ __  __  ____   ___      _________________________________________
||   || ||  || ||  || ||__      Hugs 98: Based on the Haskell 98 standard
||___|| ||__|| ||__||  __||     Copyright (c) 1994-2005
||---||         ___||           World Wide Web: http://haskell.org/hugs
||   ||                         Report bugs to: hugs-bugs@haskell.org
||   || Version: 20050308       _________________________________________

Haskell 98 mode: Restart with command line option -98 to enable extensions

Type :? for help
Main> permutate' ['A','B'] 3
["AAA","AAB","ABA","ABB","BAA","BAB","BBA","BBB"]
Main> permutate' ['0','1'] 8
["00000000","00000001","00000010","00000011","00000100","00000101","00000110","00000111","00001000","00001001","00001010","00001011","00001100","00001101","00001110","00001111","00010000","00010001","00010010","00010011","00010100","00010101","00010110","00010111","00011000","00011001","00011010","00011011","00011100","00011101","00011110","00011111","00100000","00100001","00100010","00100011","00100100","00100101","00100110","00100111","00101000","00101001","00101010","00101011","00101100","00101101","00101110","00101111","00110000","00110001","00110010","00110011","00110100","00110101","00110110","00110111","00111000","00111001","00111010","00111011","00111100","00111101","00111110","00111111","01000000","01000001","01000010","01000011","01000100","01000101","01000110","01000111","01001000","01001001","01001010","01001011","01001100","01001101","01001110","01001111","01010000","01010001","01010010","01010011","01010100","01010101","01010110","01010111","01011000","01011001","01011010","01011011","01011100","01011101","01011110","01011111","01100000","01100001","01100010","01100011","01100100","01100101","01100110","01100111","01101000","01101001","01101010","01101011","01101100","01101101","01101110","01101111","01110000","01110001","01110010","01110011","01110100","01110101","01110110","01110111","01111000","01111001","01111010","01111011","01111100","01111101","01111110","01111111","10000000","10000001","10000010","10000011","10000100","10000101","10000110","10000111","10001000","10001001","10001010","10001011","10001100","10001101","10001110","10001111","10010000","10010001","10010010","10010011","10010100","10010101","10010110","10010111","10011000","10011001","10011010","10011011","10011100","10011101","10011110","10011111","10100000","10100001","10100010","10100011","10100100","10100101","10100110","10100111","10101000","10101001","10101010","10101011","10101100","10101101","10101110","10101111","10110000","10110001","10110010","10110011","10110100","10110101","10110110","10110111","10111000","10111001","10111010","10111011","10111100","10111101","10111110","10111111","11000000","11000001","11000010","11000011","11000100","11000101","11000110","11000111","11001000","11001001","11001010","11001011","11001100","11001101","11001110","11001111","11010000","11010001","11010010","11010011","11010100","11010101","11010110","11010111","11011000","11011001","11011010","11011011","11011100","11011101","11011110","11011111","11100000","11100001","11100010","11100011","11100100","11100101","11100110","11100111","11101000","11101001","11101010","11101011","11101100","11101101","11101110","11101111","11110000","11110001","11110010","11110011","11110100","11110101","11110110","11110111","11111000","11111001","11111010","11111011","11111100","11111101","11111110","11111111"]
Main> :q
[Leaving Hugs]
languitar@Little-Tux:~/Desktop >