* A question regarding certain rules
@ 2017-10-09 17:41 Dimitris Tsementzis
2017-10-09 17:54 ` [HoTT] " Gaëtan Gilbert
0 siblings, 1 reply; 3+ messages in thread
From: Dimitris Tsementzis @ 2017-10-09 17:41 UTC (permalink / raw)
To: Homotopy Type Theory
Dear all,
Is there a type theory that has been considered in the literature which includes *both* the following rules
Γ |- t : T
———————— (R1)
Γ |- t : C(T)
Γ |- t : T
———————— (R2)
Γ |- p(t) : C(T)
where C(T) is a type expression, p(t) is a term expression, t is a term expression that must appear in p(t), and T is a type expression that may or may not appear in C(T).
An example of (R1) is (U-CUMUL) as in the HoTT book, i.e. cumulativity of universes.
An example of (R2) is (Nat-intro-2) as in the HoTT book, i.e. the successor for Nat (with C(T) == Nat).
Best,
Dimitris
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [HoTT] A question regarding certain rules
2017-10-09 17:41 A question regarding certain rules Dimitris Tsementzis
@ 2017-10-09 17:54 ` Gaëtan Gilbert
2017-10-10 3:06 ` Dimitris Tsementzis
0 siblings, 1 reply; 3+ messages in thread
From: Gaëtan Gilbert @ 2017-10-09 17:54 UTC (permalink / raw)
To: HomotopyTypeTheory
Does T:=Type0, C(T):=Type1, t:=nat and p(t):=nat->nat count? If so HoTT
has this. If not why not?
Gaëtan Gilbert
On 2017-10-09 19:41, Dimitris Tsementzis wrote:
> Dear all,
>
> Is there a type theory that has been considered in the literature which includes *both* the following rules
>
> Γ |- t : T
> ———————— (R1)
> Γ |- t : C(T)
>
> Γ |- t : T
> ———————— (R2)
> Γ |- p(t) : C(T)
>
> where C(T) is a type expression, p(t) is a term expression, t is a term expression that must appear in p(t), and T is a type expression that may or may not appear in C(T).
>
> An example of (R1) is (U-CUMUL) as in the HoTT book, i.e. cumulativity of universes.
>
> An example of (R2) is (Nat-intro-2) as in the HoTT book, i.e. the successor for Nat (with C(T) == Nat).
>
> Best,
>
> Dimitris
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [HoTT] A question regarding certain rules
2017-10-09 17:54 ` [HoTT] " Gaëtan Gilbert
@ 2017-10-10 3:06 ` Dimitris Tsementzis
0 siblings, 0 replies; 3+ messages in thread
From: Dimitris Tsementzis @ 2017-10-10 3:06 UTC (permalink / raw)
To: Gaëtan Gilbert; +Cc: Homotopy Type Theory
Thanks. Yes, this is of course entirely compatible with my description, yet I am not sure it captures what I was after.
I will have to think more about whether your example suffices for my purposes.
Dimitris
> On Oct 9, 2017, at 13:54, Gaëtan Gilbert <gaetan....@skyskimmer.net> wrote:
>
> Does T:=Type0, C(T):=Type1, t:=nat and p(t):=nat->nat count? If so HoTT has this. If not why not?
>
> Gaëtan Gilbert
>
> On 2017-10-09 19:41, Dimitris Tsementzis wrote:
>> Dear all,
>> Is there a type theory that has been considered in the literature which includes *both* the following rules
>> Γ |- t : T
>> ———————— (R1)
>> Γ |- t : C(T)
>> Γ |- t : T
>> ———————— (R2)
>> Γ |- p(t) : C(T)
>> where C(T) is a type expression, p(t) is a term expression, t is a term expression that must appear in p(t), and T is a type expression that may or may not appear in C(T).
>> An example of (R1) is (U-CUMUL) as in the HoTT book, i.e. cumulativity of universes.
>> An example of (R2) is (Nat-intro-2) as in the HoTT book, i.e. the successor for Nat (with C(T) == Nat).
>> Best,
>> Dimitris
>
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