combinatorics in ruby with hashes

Question

Is there a built in function or convention for when you want to do combinations of states concisely?

Given the following:

{
  animal: [:dog, :cat],
  disposition: [:grumpy, :hungry, :sleepy]
}

I want to make:

[
  {animal: :dog, disposition: :grumpy},
  {animal: :dog, disposition: :hungry},
  {animal: :dog, disposition: :sleepy},
  {animal: :cat, disposition: :grumpy},
  {animal: :cat, disposition: :hungry},
  {animal: :cat, disposition: :sleepy}
]

taking any number of input states, i.e. more than 2.

Others must have solved this before me in an elegant fashion?

Python has an array way of doing it here

Answer 1

This SO answer should work.

[{:animal=>:dog, :disposition=>:grumpy}, {:animal=>:dog, :disposition=>:hungry}, {:animal=>:dog, :disposition=>:sleepy}, {:animal=>:cat, :disposition=>:grumpy}, {:animal=>:cat, :disposition=>:hungry}, {:animal=>:cat, :disposition=>:sleepy}]

Answer 2

intial hash:

a={  
  animal: [:dog, :cat],  
  disposition: [:grumpy, :hungry, :sleepy]  
}  
b= a[:animal].product(a[:disposition]).collect do |c|
  {animal: c[0], disposition: c[1]}
end