if (a = b or a = c or a = d or a = f)

in a shorter, easier to view

   if [b,c,d,f].include?(a)

David

That's gorgeous, thanks! Works brilliantly.

You can, of course, use variables instead of literals, ala

David

also take a look at #any? and #all?

they come in handy in situations like,

if a < b or a < c or a < d

if a > b and a > c and a > d

sometimes, you may want a reverse to #include? behavior so that you'd like to emphasize first the element as compared to the collection. something like,

a.in?[b,c,d,f]

a = [b,c,d,e,f].compact.first

b=c=d=false
e=f = 99
a1 = [b,c,d,e,f].compact.first
a2=b or a2=c or a2=d or a2=e or a2=f
puts a1, a2

a1 is false and a2 is 99

  case 1..3
    when 1..3: puts 'yay!'
    else       puts 'boo'
  end

results in "boo", because (1..3) === (1..3) #=> false

Still, as the docs for Object#=== say:
"For class Object, effectively the same as calling #==, but typically
overridden by descendants to provide meaningful semantics in case
statements."

Numbers, strings, arrays, hashes, booleans...all these treat === as
==. I'm not arguing that they should be treated the same, or that we
should sweep the difference under the rug. I'm simply suggesting that
if you know the difference between #== and #===, particularly on the
objects that you place in your case statements, then under many
circumstances you can use a case statement as a convenience for
checking equality on many objects at once.

  if a = (b or c or d or f)