Question

Let me preface this with saying that I am new to Ruby.

I was trying to do something like this:

raise NoSuchStrategyError unless ((player1[1].downcase && player2[1].downcase) == ( "p" || "r" || "s"))

However it was not working as intended. It only recognized if the first argument was a “p”. If it was an “r” or an “s” it threw the error. I had to write it out the long way like this for it to work:

raise NoSuchStrategyError unless player1[1].downcase == "p" or player1[1].downcase == "s" or player1[1].downcase == "r"
raise NoSuchStrategyError unless player2[1].downcase == "p" or player2[1].downcase == "s" or player2[1].downcase == "r"

Is there a better way to do this shorthand?

Answer 1

This is because || returns the first argument to it that is truthy. In this case, since "p" is truthy, ("p" || "r" || "s") always returns "p". Knowing this, your first statement can be equivalently rewritten as:

raise NoSuchStrategyError unless ((player1[1].downcase && player2[1].downcase) == "p"

As Blender hinted at in his comment about Python, you can do:

raise NoSuchStrategyError unless ['p', 'r', 'y'].include?(player1[1].downcase) && ['p', 'r', 'y'].include?(player2[1].downcase)

or more concisely:

raise NoSuchStrategyError unless [player1[1].downcase, player2[1].downcase].all? { |c| %w[p r s].include? c }

Additionally, be careful when using and & or in Ruby, they are different than && & ||. You can (and should) read more about the difference.