Unanswered Questions
73 questions with no upvoted or accepted answers
23
votes
0
answers
571
views
Categorical semantics of Agda
I would like to know the state of the art regarding the categorical semantics of the type theory implemented by Agda — or at least some approximation of that type theory that is amenable to ...
- 3,200
13
votes
0
answers
369
views
Unintentionally proven false theorem with type-in-type outside logic and foundations?
We are all familiar with Russell's paradox, and it is known that Per Martin-Löf proved that type-in-type is normalizing and consistent (which is false), by accidentally using an assumption in his meta-...
12
votes
0
answers
169
views
Rules for mutual inductive/coinductive types
Some proof assistants, like Agda and maybe Coq, allow families of mutually defined types, or nested definitions of types, in which some are inductive and others are coinductive. I have no idea what ...
- 3,200
10
votes
0
answers
187
views
Is there a proof assistant (or an embedding) for the (co)end calculus?
A Higher-Order Calculus for Categories describes a system where you can conveniently perform manipulations with categories, functors, Yoneda embeddings etc. An example of the rules is: $$\frac{\Gamma ,...
- 2,846
9
votes
0
answers
309
views
Alternatives to universe levels
All of the type theory based proof assistants that I have seen have an infinite hierarchy of type universes to avoid the type of types being a term of itself. Are there alternative systems which could ...
- 91
7
votes
0
answers
83
views
How do I write a minimal working example (MWE) in Coq to demonstrate some problem?
To get help with some incomplete proof script or definition in Coq, or demonstrate some failing (e.g., Ltac) tactic or command, I am often asked to write a minimal working example (MWE) of Coq ...
- 425
7
votes
0
answers
195
views
What was the first proof assistant with eta equality for records?
The Agda language supports eta equality for (non-(co)inductive) record types:
...
- 506
6
votes
0
answers
173
views
Coq - Are there functions which are provably equal but not definitionally equal?
In Coq, are there types A,B and functions f, g : A -> B such that f = g propositionally ...
6
votes
0
answers
120
views
In VSCoq, how to issue an arbitrary Gallina query via the prompt?
I’m currently trying out Visual Studio + VSCoq, having previously used Emacs + Proof General for Coq, and there’s one part of my usual workflow that I haven’t managed to replicate yet. Is there a way ...
6
votes
0
answers
84
views
What are Generic Arguments in Coq and how are they structured in their OCaml code?
I was trying to figure out why it seems that in a Coq generic argument there seems to be 3 arguments to the constructor GenArg when according to me there should ...
- 9,195
6
votes
0
answers
192
views
How does one systematically traverse OCaml representations of Coq ASTs terms?
I want to be able to (tree) traverse Coq terms (e.g. in OCaml or using their s-expression representation in any language).
My main challenge is to figure out how to do this systematically because I ...
- 136
6
votes
0
answers
137
views
How to write heavily indexed proofs?
I've been playing with hereditary substitution. However, things get very awkward because substitution isn't total unless you index by the environment somehow.
In my old approach terms were not indexed ...
- 2,868
6
votes
0
answers
114
views
Is every logical theory embeddable in a dependently typed extensional type theory?
In category theory by the Yoneda embedding every category $\mathcal{C}$ is a subcategory of a category of presheafs $[\mathcal{C}^{\text{op}}, \text{Set}]$. Every category of presheafs is a topos and ...
- 2,868
5
votes
0
answers
246
views
Mere propositions and Consistency with Impredicativity, Excluded Middle and Large Elimination
Setup
Current Understanding
I've recently been trying to learn about the interaction of Impredicative Polymorphism, Large Elimination and Excluded Middle (notably, inconsistency). Notably, this is ...
- 73
5
votes
0
answers
111
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Display style proofs using Coq
How to display proofs using in Gentzen tree style and (or) Fitch-style, using CoqIDE or JsCoq?
PS: I'm rookie used coq.
- 2,300