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

score 2 · Answer 1 · answered Jan 14 '14 at 10:47

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

answered Jan 14 '14 at 10:47

rejin

179
1
13

score 1 · Accepted Answer · edited May 23 '17 at 11:49

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}]

edited May 23 '17 at 11:49

Community

1
1

answered Jan 14 '14 at 10:33

Ju Liu

3,939
13
18

combinations = input.values[0].product(*input.values[1..-1]).map{|p| Hash[input.keys.zip p]} – xxjjnn Jan 14 '14 at 10:53

combinatorics in ruby with hashes

2 Answers2