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Power set: Difference between revisions
Added Elixir
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It would also be possible to define an object which is the powerset of a provided set without actually instantiating all of its members immediately. [[Category:E examples needing attention]]
=={{header|Elixir}}==
{{trans|Erlang}}
<lang elixir>defmodule RC do
use Bitwise
def powerset1(list) do
n = length(list)
max = round(:math.pow(2,n))
for i <- 0..max-1, do: (for pos <- 0..n-1, band(i, bsl(1, pos)) != 0, do: Enum.at(list, pos) )
end
def powerset2([]), do: [[]]
def powerset2([h|t]) do
pt = powerset2(t)
(for x <- pt, do: [h|x]) ++ pt
end
def powerset3([]), do: [[]]
def powerset3([h|t]) do
pt = powerset3(t)
powerset3(h, pt, pt)
end
defp powerset3(_, [], acc), do: acc
defp powerset3(x, [h|t], acc), do: powerset3(x, t, [[x|h] | acc])
end
IO.inspect RC.powerset1([1,2,3])
IO.inspect RC.powerset2([1,2,3])
IO.inspect RC.powerset3([1,2,3])
IO.inspect RC.powerset1([])
IO.inspect RC.powerset1(["one"])</lang>
{{out}}
<pre>
[[], [1], [2], [1, 2], [3], [1, 3], [2, 3], [1, 2, 3]]
[[1, 2, 3], [1, 2], [1, 3], [1], [2, 3], [2], [3], []]
[[1], [1, 3], [1, 2, 3], [1, 2], [2], [2, 3], [3], []]
[[]]
[[], ["one"]]
</pre>
=={{header|Erlang}}==
Line 2,556 ⟶ 2,597:
<lang ruby># Based on http://johncarrino.net/blog/2006/08/11/powerset-in-ruby/
# See the link if you want a shorter version.
# This was intended to show the reader how the method works.
class Array
# Adds a power_set method to every array, i.e.: [1, 2].power_set
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