| definition: |
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)
|
| demand: |
no demanded arguments |
| deterministic: |
deterministic operation |
| documentation: |
--- Returns the list of all permutations of the argument. |
| failfree: |
_ |
| indeterministic: |
referentially transparent operation |
| infix: |
no fixity defined |
| iotype: |
{(_) |-> {:}}
|
| name: |
permutations |
| precedence: |
no precedence defined |
| result-values: |
{:}
|
| signature: |
[a] -> [[a]] |
| solution-complete: |
operation might suspend on free variables |
| terminating: |
possibly non-terminating |
| totally-defined: |
reducible on all ground data terms |