CurryInfo: base-3.4.0 / Data.List.permutations

 
permutations           :: [a] -> [[a]]
permutations xs0       =  xs0 : perms xs0 []
 where
  perms []     _  = []
  perms (t:ts) is = foldr interleave (perms ts (t:is)) (permutations is)
    where interleave    xs     r = let (_, zs) = interleave' id xs r in zs
          interleave' _ []     r = (ts, r)
          interleave' f (y:ys) r = let (us, zs) = interleave' (f . (y:)) ys r
                                   in (y:us, f (t:y:us) : zs)

 no demanded arguments

 deterministic operation

 
Returns the list of all permutations of the argument.

 _

 referentially transparent operation

 no fixity defined

 {(_) |-> {:}}

 permutations

 no precedence defined

 {:}

 [a] -> [[a]]

 operation might suspend on free variables

 possibly non-terminating

 reducible on all ground data terms