How can one have a function that uses a dynamic amount of each
statements? Below is the code for level 3. Is there a way to define this
easily using recursion? I want to avoid having a separate function for
each level.

That function does not give the correct output for larger arrays. The
level functions can be generated with eval, see the code below. However
there must be a better Ruby way.

tmp.push “nums.each{ |n#{num}| tmp.push #{str}\n”
p calcd(array)

def calc_new(arr,l)
h,t = Hash[*(0…arr.size).zip(arr).flatten],[]
(1…l).each do |z|
(0…arr.size**l).each do |x|
t << x.to_s(arr.size).rjust(z,“0”)
end
end
t.uniq.sort.map{|c| c.split(//).map{|d| h[d.to_i]}.join}
end

def calc_new(arr,l)
h,t = Hash[*(0…arr.size).zip(arr).flatten],[]
p h
(1…l).each do |z|
(0…arr.size**l).each do |x|
t << x.to_s(arr.size).rjust(z,“0”)
end
end
t.uniq.sort.map{|c| c.split(//).map{|d| h[d.to_i(arr.size)]}.join}
end

That code does work well for array.size <= 36, however I need a dynamic
amount without an arbitrary limitation.

The data set causes an illegal radix ArgumentError since it is indeed >
36. Using eval any array size can be handled. I may just use Java if a
robust solution is not possible in Ruby without resorting to eval.

what are you trying to accomplish? Permutations maybe?
I frankly can’t think of a problem that I would solve using them.

One application is exhaustive, brute-force unit testing. For example,
in my eRuby processor, it was necessary to test proper handling of
eRuby directives surrounded by various amounts and kinds of whitespace
(empty string, spaces, tabs, and line breaks):

what are you trying to accomplish? Permutations maybe?
I frankly can’t think of a problem that I would solve using them.

One application is exhaustive, brute-force unit testing. For example,
in my eRuby processor, it was necessary to test proper handling of
eRuby directives surrounded by various amounts and kinds of whitespace
(empty string, spaces, tabs, and line breaks):

To be fair, my library also implements combinations and
enumerations: both in the “n choose k” subset form and in the exhaustive
“all items in this list” form.

It’s interesting to note that the only algorithmic difference between
permutations and combinations is that combinations prevent already
visited vertices from being visited again in subsequent iterations,
whereas permutations do not. I was quite pleased with this observation,
because it allowed me to base nPk and nCk on a single implementation:
pnk_cnk_impl().

def permutations li
if li.length < 2
yield li
else
?> li.each do |element|
?> permutations(li.select() {|n| n != element})
?> {|val| yield([element].concat val)}

end
end

end
=> nil

permutations [“0”, “1”]
LocalJumpError: no block given
from (irb):7:in permutations' from (irb):3:inpermutations’
from (irb):6:in permutations' from (irb):5:ineach’
from (irb):5:in `permutations’
from (irb):12

permutations [“0”, “1”] do end
=> [“0”, “1”]

permutations [“0”, “1”] do |val| val end
=> [“0”, “1”]

permutations [“0”, “1”, “2”] do end
=> [“0”, “1”, “2”]

permutations [“0”, “1”, “2”] do |val| val end
=> [“0”, “1”, “2”]

permutations [“0”, “1”, “2”] do |val| [val] end
=> [“0”, “1”, “2”]

if length < 2
yield self
else
each do |element|
select { |candidate|
candidate != element
}.permutations { |smaller|
yield [element, *smaller]
}
end
end