Ruby Array#product method behaviour when given a block

Question

In Ruby, what does the Array#product method do when given a block? The documentation says "If given a block, product will yield all combinations and return self instead." What does it mean to yield all combinations? What does the method do with the given block?

Answer 1

By "yield all combinations" it means that it will yield (supply) all combinations of elements in the target (self) and other (argument) arrays to the given block.

For example:

a = [1, 2]
b = [:foo, :bar]
a.product(b) { |x| puts x.inspect } # => [1, 2]
# [1, :foo]
# [1, :bar]
# [2, :foo]
# [2, :bar]

It is roughly equivalent to this function:

class Array
  def yield_products(other)
    self.each do |x|
      other.each do |y|
        yield [x, y] if block_given?
      end
    end
  end
end