Zulip Chat Archive

Stream: Type theory

Topic: Indexed QPF


Palalansoukî (Nov 08 2025 at 08:58):

QPF.Fix provides a fixed point of functor F. Can we extend this to obtain (potentially infinite) fixed points, indexed by some type? That is, by assuming appropriate conditions for F, can we properly define a constructor and destructor as follows?

variable {ι : Type u} {F : (ι  Type v)  (ι  Type v)} [IndexedQPF F]

def Fix (F : (ι  Type v)  (ι  Type v)) : ι  Type v := sorry

def Fix.mk : (i : ι)  F (Fix F) i  Fix F i := sorry

def Fix.dest : (i : ι)  Fix F i  F (Fix F) i := sorry

Last updated: Dec 20 2025 at 21:32 UTC