sequence function: or

    description:
        or(ket, ket)
        the or function
        NB: it evaluates both sequences before being passed to the 'or' function
        NB: it currently doesn't handle sequences all that well
      
    examples:
        or(|yes>, |yes>)
            |yes>
        
        or(|yes>, |no>)
            |yes>
        
        or(|no>, |no>)
            |no>
    
    see also:
      if, and, xor