I decided to write an iterator to give me all permutations of distinct elements (yes I know that there is `nthperm`

in the `Combinatorics.jl`

package).

Generators (Tasks) seem to be natural choice, so here is the code:

```
# Steinhaus–Johnson–Trotter algorithm
function all_permutations(n::Int)
elts = collect(1:n)
direction = -1*ones(Int,n)
direction[1] = 0
chosen = n
search = false
function _it()
produce(elts)
for _ in 1:factorial(n)-1
greater_chosen = find(x->x>elts[chosen], elts)
direction[[i for i in greater_chosen if i < chosen]] .= 1
direction[[i for i in greater_chosen if i > chosen]] .= -1
d = direction[chosen]
for arr in [elts, direction]
arr[chosen], arr[chosen+d] = arr[chosen+d], arr[chosen]
end
#changing directions
if chosen+d == 1 || chosen+d == n || elts[chosen+2d] > elts[chosen+d]
direction[chosen+d] = 0
search = true
end
if search == true
max = 0
chosen = 0
for i in 1:n
if elts[i] > max && direction[i] ≠ 0
max = elts[i]
chosen = i
end
end
else
chosen += d
end
produce(elts)
end
end
return Task(_it)
end
```

Code in action:

```
for i in all_permutations(3)
print(i)
end
[1,2,3][1,3,2][3,1,2][3,2,1][2,3,1][2,1,3]
```

This seems a trivial question, but why does `collect(all_permutations(3))`

returns 6-element array of identical element (`[2,1,3]`

)? (a similar application of `collect(fibtask(10)`

, as described http://slendermeans.org/julia-iterators.html, works as supposed (array of 10 consecutive Fibonacci numbers).