TUPLE: rectangle width height ;
PREDICATE: square < rectangle [ width>> ] [ height>> ] bi = ;
C: <rectangle> rectangle
C: <square> square

3 3 <rectangle>
--> 12

3 3 <square>
--> The word <square> cannot be executed because it failed to compile

Macro expansion of “boa” threw an error

The error was:
Assertion failed
got    0
expect 1

[Traceback]