Ketil Malde wrote:
Although I don't care for the cutesy naming suggested in the 'Train' datatype [...]
data TerminatedList a e = Then a (TerminatedList a e) | Finally e
(So you could do e.g: 4 `Then` 5 `Then` 1 `Finally` "success!". Of course, you might prefer symbols instead.)
I don't mind Then and Finally as constructors. The thing about the Train is not so much the suggestive constructor names Wagon/Loco or Cabin/Caboose but that the concept itself has an evocative and short name, Train . In contrast, TerminatedList feels too much like an agglomeration of technical terms to me ("weak head normal form") where the names are fairly unrelated to the actual definition. (This particularly applies to "weak", one could as well have dubbed the whole thing "blue head normal form" without any loss of meaning.) Unfortunately, TerminatedList is also too long for extended use in type signatures. Something more evocative and short, similar to the good old "queue" or "stack" would be great. How about "trail" or "track", like in data Trail a b = Then a (Trail a b) | End b the idea being that the trail of say a dog eventually leads to the dog itself. Another, not entirely serious, suggestion: ;) data Life a b = Work a (Life a b) | TheEnd b Regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com