This was (sort of) asked and addressed a while back at What are typeglobs (useful for)?. I was introduced to the Union data structure in my college compiler class for what it is worth. I have always thought of typeglobs as Unions -- things that can store the same value but reference/use it in different ways. I'm probably wrong, however. :)

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)