Question

I have an array of arrays like so: [[1, "dog"], [2, "cat"], [2, "bird"], [3, "monkey"]]. I want to check whether the larger array contains arrays of a given number without regard to the animal element of the array. I also do not want to loop through the array because this would become computationally heavy.

So something like @boolean = bigArray.include?([2, *]), except something that actually works…

Answer 1

You have two possible solutions. Detect the element in the array or convert the array into a Hash

1. Use Enumerable#detect, it will stop as soon as it finds a match and return it, nil otherwise.

> a = [[1, "dog"], [2, "cat"], [2, "bird"], [3, "monkey"]]
 => [[1, "dog"], [2, "cat"], [2, "bird"], [3, "monkey"]] 
> a.detect{ |(n, _)| n == 2 }
 => [2, "cat"]
> a.detect{ |(n, _)| n == 10 }
 => nil 

If you want to add this to the Array class like your example, and force it to return a boolean, do this:

class Array
  def custom_include?(num)
    !!detect{ |(n, _)| num == n }
  end
end

Example:

> a.custom_include?(2)
 => true 
> a.custom_include?(10)
 => false

2. If you don’t care about the colliding keys, you could convert the array into a Hash and see if the key exists.

> a = [[1, "dog"], [2, "cat"], [2, "bird"], [3, "monkey"]]
 => [[1, "dog"], [2, "cat"], [2, "bird"], [3, "monkey"]] 
> Hash[a][2]
 => "bird"
> Hash[a][10]
 => nil