Cartesian and polar coordinates library

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1.cartesian product of arrays

Hello,

did I miss some standard library function? Anyway, then I'll do it on
my own:

def cartprod(*args)
  result = [[]]
  while [] != args
    t, result = result, []
    b, *args = args
    t.each do |a|
      b.each do |n|
        result << a + [n]
      end
    end
  end
  result
end

Example:
cartprod([1,2],[3,4,5],[6,7,8])
=> [[1, 3, 6], [1, 3, 7], [1, 3, 8], [1, 4, 6], [1, 4, 7], [1, 4, 8],
    [1, 5, 6], [1, 5, 7], [1, 5, 8], [2, 3, 6], [2, 3, 7], [2, 3, 8],
    [2, 4, 6], [2, 4, 7], [2, 4, 8], [2, 5, 6], [2, 5, 7], [2, 5, 8]]

Regards
  Thomas

2.cartesian product - next to last version

Hello,

Since the original thread got a little long, I decided to post my next to 
last version in a new thread. My previous version gave results like 
[[1,4],7] for more than two arrays when you really wanted [1,4,7]. The trick 
is to flatten each element of the product. The following works for any 
number of arrays. Of course you might want a product in which the elements 
of that product are arrays. Any suggestions?

class Array

  def cartprod(b=[])
    if b.empty? then
      #assume self an array of arrays
      inject {|cp,x| cp.cartprod(x) }
    else
      z = inject([]) {|a,x| b.inject(a) {|a,y| a << [x,y]}}
      z.collect! {|x| x.flatten }
    end
  end

end


a=[1,2,3]
b=[4,5,6]
c=[7,8,9]

# works fine
p [a,b,c].cartprod

# doesn't work since [1,4,7,[10,11]] is [1,4,7,10,11]
d=[10, [11,12]]
p [a,b,c,d].cartprod

3.cartesian product

Hello,

How would I create a function that will take list (array) of integers and 
return their cartesian product?

Thank You,

Walter Kehowski
nuby 

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