Show how proc aliases === to call

case_and_proc.rb

# On procs, Ruby aliases `===` to `call`
# The comparator that a case statement uses is `===`
# This means that you can use procs as when clauses

a_proc = proc { "I'm a proc" }
b_proc = proc {|x| "I'm a proc that says '#{x}'"}

a_proc.call  # => I'm a proc
b_proc.call  # => I'm a proc that says ''
b_proc.call "Hello!" #=> I'm a proc that says 'Hello!'

a_proc.===  #=> I'm a proc
b_proc.===  #=> I'm a proc that says ''
b_proc.=== "So long!" #=> I'm a proc that says 'So long!'


c_proc = proc {|x| x && x }

c_proc.call(true) #=> true
c_proc.call(false) #=> false

c_proc.===(true) #=> true
c_proc.===(false) #=> false


@multi_of_5 = proc {|x| x % 5 == 0 }
@multi_of_3 = proc {|x| x % 3 == 0 }

def check_multi(n)
  case n
  when @multi_of_5
    "Its definitely a multiple of 5"
  when @multi_of_3
    "Its definitely a multiple of 3"
  else
    "No clue what's up with #{n}"
  end
end

check_multi(4) #=> No clue what's up with 4
check_multi(6) #=> Its definitely a multiple of 3
check_multi(10) #=> Its definitely a multiple of 5


IS_US ->{|x| x.downcase.in?('us', 'usa')}
case country
when IS_US
  do_thing_with_us
end