Coq is an interactive theorem prover.

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3
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0answers
46 views

Type theoretic equivalent of isomorphism class

How one defines the notion of isomorphism class in type theory? For concreteness I will describe what I mean with an example in Coq. Suppose I have a record ToyRec: ...
4
votes
2answers
130 views

Law of excluded middle in MLTT

Is it possible to add law of excluded middle to Martin Lof Type Theory as an axiom? It seems to me, that it's possible to add it to Coq since Coq has a module for non constructive reasoning. Also, it ...
8
votes
1answer
120 views

Equality of decidable proofs?

I want to know if the decidability of equality of two decidable proofs of the same proposition can be proved without any additional axioms in Calculus of Inductive Constructions. Specifically, I want ...
7
votes
2answers
172 views

Why an infinite type hierarchy?

Coq, Agda, and Idris have an infinite type hierarchy (Type 1 : Type 2 : Type 3 : ...). But why not do it instead like λC, the system in the lambda cube that's closest to the calculus of constructions, ...
0
votes
1answer
51 views

Reverse contraposition

While it is trivial to prove contraposition ∀ A B: Prop, (A → B) → (~B → ~A) using Coq, is it equally trivial to prove the reversed form: ...
0
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2answers
95 views

How to prove that a circular prop is uninhabited?

Consider the following inductive definition of "ElProp" in coq: ...
0
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0answers
72 views

Certified program development vs. model checking

Sorry if my question is elementary but I want to know more about model checking and certified program development. What is the difference between model checking and certified program development? As ...
8
votes
3answers
795 views

Why does Coq have Prop?

Coq has a type Prop of proof irrelevant propositions which are discarded during extraction. What are the reason for having this if we use Coq only for proofs. Prop is impredicative, so Prop : Prop, ...
15
votes
2answers
664 views

Why do Agda and Coq disagree on strict positivity?

I've stumbled across a confusing disagreement between Agda and Coq that is not obviously related to the most well known distinctions between their type theories (e.g., (im)predicativity, ...
4
votes
1answer
235 views

Induction over a transitive relation in Coq

I have the current problem when using induction with Coq: I have states ST, which are pairs (A,B), where A are Addresses (nat) and B are Memories (A parameter) ...
3
votes
1answer
422 views

Defining Mutually Recursive functions in Coq

This question is related to (but not the same as): How to define a function inductively on two arguments in Coq? In particular, I used those techniques (defining a second fixed point function) and ...
5
votes
1answer
165 views

How to describe the set of “all computable functions” using Coq?

Would the set of all computable functions be just the set of all maps of the form f : forall n : nat, P n -> nat where ...
-1
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1answer
197 views

problem in embedding

I want to embed PPTL(a kind of logic) in Coq. Because of its complex semantics, I just embed its systax. ...
1
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0answers
278 views

Encoding a logic in Coq

I want to encode a logic into Coq. The semantics of the logic are very complex and I just want to encode the syntax, axioms, inference rules. I use deep embedding, but I can't use notation like: ...
-2
votes
1answer
341 views

Coq definition with unusual syntax (Definition … Defined.)

While examining the package Library ZFC.Sets, I found the following definition: ...
9
votes
1answer
366 views

Has the compactness theorem for FOL been formalized in Coq/Isabelle/etc?

I've been searching for a formalization of the compactness theorem for FOL, but haven't found any. Is anyone aware of such a development or related work?
15
votes
1answer
623 views

Class of functions computable by Coq

Since it does not allow nonterminating computation, Coq is necessarily not Turing-complete. What is the class of functions that Coq can compute? (is there an interesting characterization thereof?)
10
votes
3answers
458 views

Modeling objects (OOP) in dependent type theory

I am interested in modeling objects, from object oriented programming, in dependent type theory. As a possible application, I would like to have a model where I can describe different features of ...
6
votes
1answer
559 views

How to use induction without Fixpoint definition in Coq?

I want to verify a program written in C. I am using Jessie to translate the (pre/post)conditions of the program to Coq. In Coq I will make a proof. Sometimes I need recursive definitions. ...
0
votes
1answer
405 views

Proving that inclusion is antisymmetric in Coq

I'm a Coq newbie and I'd like to prove that the inclusion relation is antisymmetric, that is: $\forall x\forall y(x\subseteq y\land y\subseteq x\rightarrow x=y)$. I wrote the following thing: ...
9
votes
2answers
237 views

Does the order of declarations in an inductive type matter?

I was wondering if the order of declarations of an inductive type can matter. For example in Coq you can define Nat either by: ...
13
votes
3answers
690 views

What is the role of predicativity in inductive definitions in type theory?

We often want to define an object $A \in U$ according to some inference rules. Those rules denote a generating function $F$ which, when it is monotonic, yields a least fixed point $\mu F$. We take $A ...
17
votes
3answers
975 views

How would I go about learning the underlying theory of the Coq proof assistant?

I'm going over the course notes at CIS 500: Software Foundations and the exercises are a lot of fun. I'm only at the third exercise set but I would like to know more about what's happening when I use ...
11
votes
1answer
980 views

Prove proof irrelevance in Coq?

Is there a way to prove the following theorem in Coq? Theorem bool_pirrel : forall (b : bool) (p1 p2 : b = true), p1 = p2. EDIT: An attempt to give a brief ...
17
votes
1answer
701 views

Where is the proof that Coq + Excluded Middle is consistent

I've seen (and heard) it claimed that it is safe to add the classical axiom of excluded middle to Coq, but I can not seem to find a paper supporting this claim. The papers I see listed on the Coq wiki ...
2
votes
2answers
239 views

formalizing a statement about the expressive power of programming languages wrt divergence

In the Coq'Art book the authors mention in passing that any language that can calculate all computable functions must also be able to express diverging computations. Or in other words, there can be no ...
9
votes
1answer
2k views

How to define a function inductively on two arguments in Coq?

How can I convince Coq that the recursive function given below terminates? The function takes two inductive arguments. Intuitively, the recursion terminates because either argument is decomposed. ...
34
votes
3answers
2k views

Shallow versus Deep Embeddings

When encoding a logic into a proof assistant such as Coq or Isabelle, a choice needs to be made between using a shallow and a deep embedding. In a shallow embedding logical formulas are written ...
13
votes
2answers
617 views

Eliminating cofix in Coq proof

While trying to prove some basic properties using coinductive types in Coq, I keep running into the following problem and I cannot get around it. I've distilled the problem into a simple Coq script as ...