[Pharo-dev] powerSet

[stepharo]

Hi

I was programming an exercise with one of my son (well in Python.... 
arghhhhhh)
and I end it up doing it in Pharo (I'm save now).
The idea was to write one function that computes the powerset

powerset(4)
    = a Set(a Set(1) a Set(1 2) a Set(3) a Set(2) a Set(1 3) a Set(2 3) 
a Set(1 2 3) a Set(4) a Set(1 4) a Set(2 4) a Set(1 2 4) a Set(3 4) a 
Set(1 3 4) a Set(2 3 4) a Set(1 2 3 4))

I did it without thinking too much in fact

| s n ps |
ps := Set new.

1 to: ((2 raisedTo: 4) -1)
    do: [ :i |
        s := Set new.
        n := 0.
        1 to: 4 do: [ :b |
            n := n + 1.
            ((i bitAt: b) = 1 )
                ifTrue: [ s add: n].
            ps add: s ]].
ps

but I wonder if we want to add it to our lib.

Stef