Abbreviated names for Duration values when written as Haskell literals. There are letter names where w is whole_note and so on, and numerical names where _4 is quarter_note and so on. In both cases a ' extension means a dot so that e'' is a double dotted eighth_note. The prefix is _ not d since d4 etc. are also note names.

zipWith duration_compare_meq [e,e,e,e'] [e,s,q,e] == [EQ,GT,LT,GT]
zipWith sum_dur [e,q,q'] [e,e,e] == [Just q,Just q',Just h]
zipWith sum_dur' [e,q,q'] [e,e,e] == [q,q',h]