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Wired program type checked. #51

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molikto opened this issue Aug 31, 2016 · 1 comment
Open

Wired program type checked. #51

molikto opened this issue Aug 31, 2016 · 1 comment

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@molikto
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molikto commented Aug 31, 2016

test1 (t: nat): U = nat

test2 (a: nat): U = 
    (test1 a)
   where
    a: (test2 zero) = zero

An equivalent program doesn't type check in Coq

@molikto molikto changed the title Wired problem type checked. Wired program type checked. Aug 31, 2016
@coquand
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coquand commented Aug 31, 2016

Thanks for the example.

I am not sure it should type-check however.
The type-checking of a recursive definition

x : A = t

should be

x : A |- t : A (1)

For simplifying the implementation of HIT, we changed this to

x : A = t |- t : A (2)

but we have to think more which one (1) or (2) should be used
for recursive definitions.

On 31 Aug 2016, at 06:37, Minghao Liu [email protected] wrote:

test1 (t: nat): U = nat

test2 (a: nat): U =
(test1 a)
where
a: (test2 zero) = zero
An equivalent problem doesn't type check in Coq


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