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remove question - I tried and it doesn't improve the universes
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martinescardo committed Oct 21, 2024
1 parent 03e52d5 commit 61a7059
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31 changes: 30 additions & 1 deletion source/InjectiveTypes/Blackboard.lagda
Original file line number Diff line number Diff line change
Expand Up @@ -556,7 +556,7 @@ retract-of-ainjective : (D' : 𝓦' ̇ ) (D : 𝓦 ̇ )
→ ainjective-type D 𝓤 𝓥
→ retract D' of D
→ ainjective-type D' 𝓤 𝓥
retract-of-ainjective D' D i (r , (s , rs)) {X} {Y} j e f = φ a
retract-of-ainjective D' D i (r , s , rs) {X} {Y} j e f = φ a
where
a : Σ f' ꞉ (Y → D) , f' ∘ j ∼ s ∘ f
a = i j e (s ∘ f)
Expand Down Expand Up @@ -1779,6 +1779,35 @@ Here are some corollaries:

\end{code}

Added 21st October 2024.

\begin{code}

aflabby-embedding-retract : (D : 𝓤 ̇ ) (Y : 𝓥 ̇ ) (j : D → Y)
→ is-embedding j
→ aflabby D (𝓤 ⊔ 𝓥)
→ retract D of Y
aflabby-embedding-retract D Y j e a =
embedding-retract D Y j e (aflabby-types-are-ainjective D a)

retract-of-aflabby : (D : 𝓤 ̇ ) (E : 𝓥 ̇ )
→ aflabby D 𝓣
→ retract E of D
→ aflabby E 𝓣
retract-of-aflabby D E D-aflabby (r , s , rs) P P-is-prop f
= r d ,
(λ (p : P) → r d =⟨ ap r (I p) ⟩
r (s (f p)) =⟨ rs (f p) ⟩
f p ∎)
where
d : D
d = aflabby-extension D-aflabby (P , P-is-prop) (s ∘ f)

I : (p : P) → d = s (f p)
I = aflabby-extension-property D-aflabby (P , P-is-prop) (s ∘ f)

\end{code}

Fixities:

\begin{code}
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3 changes: 0 additions & 3 deletions source/InjectiveTypes/Subtypes.lagda
Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,3 @@ module _ (D : 𝓤 ̇ )

TODO. Can the above logically equivalence be made into a type
equivalence?

TODO. Perhaps using aflabbiness we would get more general universe
levels.

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