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[Coq-Club] Universe of Types / Internals


Chronological Thread 
  • From: t x <txrev319 AT gmail.com>
  • To: coq-club <coq-club AT inria.fr>
  • Subject: [Coq-Club] Universe of Types / Internals
  • Date: Sun, 17 Nov 2013 23:41:22 -0800

Thoughts:

Although Coq displays the following:
(1) cons: forall (A: Type) (lst: list A) (x: A), list A


we know this is a "lie" since Coq has a universe tower rather than a type of types.


Thus, it seems internally, this must be stored as:
(2) cons: forall (k: Coq-internal-Int) (A: universe k) (lst: list A) 9x: A), list A


Now, we can't have (2) in Coq since "defining Natural numbers requires Type" so we can't have
"k:Nat"
and must instead have
"k: Coq-internal-int"


Question:

Is the above analysis correct? If not, how else does Coq get around the fact that "[Universe k] is always displayed as Type" and "having a Type of Type -> paradox."

Thanks!



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