predicates
   action(integer)

clauses
   action(1) :- !,
      write("You typed 1.").

   action(2) :- !,
      write("You typed two.").

   action(3) :- !,
      write("Three was what you typed.").

   action(_) :- !,
      write("I don't know that number!").

goal
   write("Type a number from 1 to 3: "),
   readreal(Choice), 
   action(Choice).