Question

The code below works as I want, switching a light on or off with each keypress of l. However, when I try to add other things I want done with the switching, I can’t.

look = 0
lighton = 0
while look < 10
  system 'stty cbreak'
  q = $stdin.sysread 1
  case  q ### #{q} 
  when "l" then if lighton==1 then lighton=0  and puts "ight off"
                else lighton=1 and puts "ight on" end
  end
  system 'stty cooked'
  look += 1
end #while

If I add another and it isn’t seen but I get no error:

look = 0
lighton = 0
while look <10
  system 'stty cbreak'
  q = $stdin.sysread 1
  case  q ### #{q} 
  when "l" then if lighton==1 then lighton=0  and puts "ight off" and puts "light still off"
                else lighton=1 and puts "ight on" end
  end
  system 'stty cooked'
  look += 1
end #while

I’d like to add several more statements to both the if and else portions but can’t.

Answer 1

There’s no limit, you’re just misusing the and operator. It’s not meant to do “this and that”, it does “do this and, if it is truthy, do this too”. Here’s a quick example:

1 and puts 'falsy'
nil and puts 'truthy'
# prints: falsy

Since puts returns nil, which is falsy, puts 'hello' and puts 'world' will only print “hello”.

So, don’t use and to create a one-liner. You could use ; instead, but that doesn’t help readability. Instead just use multiple lines! It’s much clearer what’s going on:

case  q
when "l"
  if lighton == 1
    lighton = 0
    puts "light off"
    puts "light still off"
  else
    lighton = 1
    puts "light on"
  end
end

You may wish to read more about and/or in Ruby and how they differ from &&/||.