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Unanswered Questions

9 questions with no upvoted or accepted answers
22 votes
0 answers
568 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 ...
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 ...
2 votes
0 answers
61 views

Elimination rules of inductive types

Why does the elimination rule of inductive types sometimes allow the target type to depend on the inductive type and sometimes not? I am confused by that. Is it correct that it makes no difference in ...
1 vote
0 answers
69 views

Heterogeneous lists, large indices

Recently I had cause to define a type of heterogeneous lists in Lean, and wrote ...
1 vote
0 answers
45 views

how to inductively define paths from paths using unimath

I'd like to define a type of graph where given a set of edges, we can define another graph that has everything from graph 1 but extends the set of edges by adding higher level edges to parallel edges(...
1 vote
0 answers
63 views

Why does Coq not allow constructor argument types to be strictly positive mutual inductive types?

Note: Apologies for the wicked mouthful of a title. I'm still getting acquainted with Coq terminology, so I might not have chosen the best words. If you have a better title suggestion, edits are more ...
1 vote
0 answers
48 views

Can you always replace mutually recursive references with parameters?

This is a follow up to a question someone else previously posted: Expressivity of mutual/nested inductives vs. regular inductives. pigworker answered that Adopting Agda-ish notation, the basic ...
1 vote
0 answers
179 views

Descriptions of heterogenous datatypes

When attempting to describe the datatype as appearing in my previous question, using indexed descriptions in style of The Gentle Art of Levitation to describe this datatype (using Agda for examples): <...
-2 votes
2 answers
118 views

Help with strong induction

I have the following definition of divisibility by 3. ...