diff --git a/12_Axioms.org b/12_Axioms.org index 0565fe9c..4da5ad5c 100644 --- a/12_Axioms.org +++ b/12_Axioms.org @@ -1185,9 +1185,9 @@ section parameter (f : A → B) parameter [inhA : inhabited A] parameter [dex : ∀ b, decidable (∃ a, f a = b)] - parameter [encB : encodable A] + parameter [encA : encodable A] parameter [deqB : decidable_eq B] - include inhA dex encB deqB + include inhA dex encA deqB definition finv : B → A := λ b : B, if ex : (∃ a, f a = b) then choose ex else arbitrary A @@ -1205,7 +1205,7 @@ end #+END_SRC The argument is essentially the same as the classical one; we have simply replaced the classical =some= with the constructive choice -function =choose=, and added three extra hypotheses: =dex=, =encB= and +function =choose=, and added three extra hypotheses: =dex=, =encA= and =deqB=. The first one makes sure we can decide whether a value =b= is in the image of =f= or not, and the last two are needed to use =choose=.