Dear all, since my post on quotient and partiality created some confusion, I want to cast some light on it from a more direct perspective.
Concerning »typedef«, we currently have two conflicting issues: a) From a foundational perspective, we want to leave »typedef« untouched »as it is« b) Recently, »typedef« in userspace became more popular (again), and there a some awkward things about it: * archaic naming, which ignores contemporary namespace conventions * sets in the specification, which is particularly silly if predicates already exist (e.g. xs \<in> {xs. distinct xs} ==> ...) * technical and difficult-to-remember syntax (do you know by heart in which order the two morphism symbols have to be written? where to place an infix syntax, or maybe even a syntax for the morphism symbols? and that (open) actually denotes that no characteristic set is defined)? * _.eqI and _.eq_iff, theorems nowadays considered fundamental (cf. Library/Dlist.thy et al.), are not proved automatically * desire to automagically register certain type properties (e.g. for the emerging lifting machinery) * (maybe you can add more) None of the b) issues is pressing on its own, but in summary I consider them critical enough to call for a solution. My idea then is the following: 1) Leave »typedef« untouched, as (internal) foundational mechanism, for bootstrap reasons (datatypes prod, sum, nat), and whenever a user thinks she needs it. 2) Provide a more convenient user-interface for user-space »typedefs« Now, if »quotient« »as it is« can cover every typedef specification, a reasonable answer would be to establish »quotient« as the canonical user-interface for non-datatype type specifications, even for cases like dlist where there is no non-trivial quotient, and resolve all those b) issues on the quotient level. Hopefully this clarifies my intention. I'm looking forward to your opinion. Cheers, Florian -- Home: http://www.in.tum.de/~haftmann PGP available: http://home.informatik.tu-muenchen.de/haftmann/pgp/florian_haftmann_at_informatik_tu_muenchen_de
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