Test whether a variable equals either one of two values

Question

I want to test whether a equals 1 or 2

I could do

a == 1 || a == 2

but this requires repeating

Answer 1

I don't know in what context you're using this in, but if it fits into a switch statement you can do:

a = 1
case a
when 1, 2
  puts a
end

Some other benefits is that when uses the case equality === operator, so if you want, you can override that method for different behavior. Another, is that you can also use ranges with it too if that meets your use case:

when 1..5, 7, 10

Answer 2

First put this somewhere:

class Either < Array
  def ==(other)
    self.include? other
  end
end

def either(*these)
  Either[*these]
end

Then, then:

if (either 1, 2) == a
  puts "(i'm just having fun)"
end

Answer 3

Your first method is idiomatic Ruby. Unfortunately Ruby doesn't have an equivalent of Python's a in [1,2], which I think would be nicer. Your [1,2].include? a is the nearest alternative, and I think it's a little backwards from the most natural way.

Of course, if you use this a lot, you could do this:

class Object
  def member_of? container
    container.include? self
  end
end

and then you can do a.member_of? [1, 2].

Answer 4

You can just use intersection like

([a] & [1,2]).present?

a alternative way.

Answer 5

Maybe I'm being thick here, but it seems to me that:

(1..2) === a

...works.

Answer 6

a.to_s()=~/^(1|2)$/