Questions tagged [inductive-type]

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5
votes
1answer
281 views

Defining inductive types in intensional type theory purely in terms of type-theoretic data

To define a (non-indexed) W-type all we need is a type $A:U$ and a function $B:A\to U$ and we get a type $W_{a:A}B(a)$. To check that this definition is valid we only need to check that the ...
6
votes
2answers
247 views

Intuition behind nested positivity and counterexamples

I'm looking at the nested positivity conditions for inductive types stated in the Coq manual. First off, are there any other references (not necessarily for Coq, but in dependent type theories ...
3
votes
0answers
87 views

Request for an update on a discussion about coinductive types in HoTT (or anywhere else)

Googling something else I stumbled on a conversation titled "coinductives" initiated by Vladimir Voevodsky on Google groups in 2014. It lasted for three days, invloved a dozen people, and ...
6
votes
0answers
146 views

Postulating self types in a proof assistant

Self types introduce two typing new rules (simplified): $ \frac{\Gamma \; \vdash \; t : [t/x]T}{\Gamma \; \vdash \; t : \iota x. T}$ I-self and $ \frac{\Gamma \; \vdash \; t : \iota x. T}{\Gamma \; \...
2
votes
0answers
49 views

Parigot encoding for F-Algebras

In this answer it is shown we can encode inductive types in System F-omega using the church encoding: $Fix F = \forall T : \mathsf{Type} \,.\, (F T \to T) \to T$ for some type constructor $F$. It ...
6
votes
0answers
109 views

Programmatic higher inductive/inductive-inductive types with equalities between equalities

I can think of practical HITs in verified software that capture some form of alpha equivalence, context equivalence or the example which defines well-typed syntax of type theory from Signatures and ...
2
votes
1answer
183 views

From Church-encoding to induction principle

I am looking for an algorithm to go from a Church-encoded datatype to their induction principle in the Calculus of Constructions. For example: ...
6
votes
2answers
205 views

How to define list zipping categorically/inductively?

Lists and fixpoints The type of $A$-lists is defined as $\mu F_A$, where $F_A(X) = 1 + A \times X$ is the "cons-or-nil"-functor and $\mu$ is the least fixpoint operator. In Haskell syntax, this would ...