((true yes) no)
the result is `yes`. Things to watch out for: the expression after the equal sign must have balanced parentheses,
-and the "in" is obligatory. The system will still produce a result, but it won't make much sense.
+and the "in" is obligatory. If you violate these rules, the system will still produce a result, but it won't make much sense.
*Abbreviations*, **NOT**: No abbreviations work. So `\xy.yxx` must be written `(\x (\y ((y x) x)))`. (As in Scheme or Racket.)