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Simplfied universe rules

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Based on better understanding of universes and predicativity after
reading Luo's ECC work.
This commit is contained in:
William J. Bowman 2015-11-10 14:11:46 -05:00
parent 548b553e43
commit 2b69999380
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GPG Key ID: DDD48D26958F0D1A
1 changed files with 14 additions and 21 deletions
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35
curnel/redex-core.rkt
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@ -39,7 +39,7 @@
| inference.
|#
(define-language ttL
(i ::= natural)
(i j k ::= natural)
(U ::= (Unv i))
(x ::= variable-not-otherwise-mentioned)
(t e ::= (Π (x : t) t) (λ (x : t) t) (elim x U) x U (t t))
@ -110,32 +110,25 @@
;;; ------------------------------------------------------------------------
;;; Universe typing
;; Types of Universes
(define-judgment-form ttL
#:mode (unv-ok I O)
#:contract (unv-ok U U)
#:mode (unv-type I O)
#:contract (unv-type U U)
[(where i_1 ,(add1 (term i_0)))
-----------------
(unv-ok (Unv i_0) (Unv i_1))])
(unv-type (Unv i_0) (Unv i_1))])
;; NB: Based on CIC predicativity rules. should be able to simplify
;; Universe predicativity rules. Impredicative in (Unv 0)
(define-judgment-form ttL
#:mode (unv-kind I I O)
#:contract (unv-kind U U U)
#:mode (unv-pred I I O)
#:contract (unv-pred U U U)
[----------------
(unv-kind (Unv 0) (Unv 0) (Unv 0))]
[----------------
(unv-kind (Unv 0) (Unv i) (Unv i))]
[----------------
(unv-kind (Unv i) (Unv 0) (Unv 0))]
(unv-pred (Unv i) (Unv 0) (Unv 0))]
[(where i_3 ,(max (term i_1) (term i_2)))
----------------
(unv-kind (Unv i_1) (Unv i_2) (Unv i_3))])
(unv-pred (Unv i_1) (Unv i_2) (Unv i_3))])
(define-metafunction ttL
[(α-equivalent? t_0 t_1)
@ -859,9 +852,9 @@
#:mode (type-infer I I I O)
#:contract (type-infer Σ Γ e t)
[(unv-ok U_0 U_1)
(wf Σ Γ)
----------------- "DTR-Axiom"
[(wf Σ Γ)
(unv-type U_0 U_1)
----------------- "DTR-Unv"
(type-infer Σ Γ U_0 U_1)]
[(where t (Σ-ref-type Σ x))
@ -874,7 +867,7 @@
[(type-infer Σ Γ t_0 U_1)
(type-infer Σ (Γ x : t_0) t U_2)
(unv-kind U_1 U_2 U)
(unv-pred U_1 U_2 U)
----------------- "DTR-Product"
(type-infer Σ Γ (Π (x : t_0) t) U)]
@ -913,7 +906,7 @@
(Π (x_3 : x_0) x_1) (Unv 0)))
(check-holds (type-infer ∅ (∅ x_0 : (Unv 0)) x_0 U_1))
(check-holds (type-infer ∅ ((∅ x_0 : (Unv 0)) x_2 : x_0) (Unv 0) U_2))
(check-holds (unv-kind (Unv 0) (Unv 0) (Unv 0)))
(check-holds (unv-pred (Unv 0) (Unv 0) (Unv 0)))
(check-holds (type-infer ∅ (∅ x_0 : (Unv 0)) (Π (x_2 : x_0) (Unv 0)) t))
(check-holds (type-check ∅ ∅ (λ (x : (Unv 0)) x) (Π (x : (Unv 0)) (Unv 0))))