Questions in category theory

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Categorical way of factoring out points

Major rewrite justifiably asked for: I'm currently trying to get a categorical way of doing something called the Gelfond-Lifschitz reduct on a set of single-headed Horn clauses. The semantics is the ...
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0answers
152 views

Category theory in plain MLTT

I want to define a category in simple MLTT (not in HoTT). I defined it with the help of setoids. I.e. category consists of: a type of objects with equivalence relation (Obj : Set) a type of arrows ...
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1answer
116 views

How can I formalize key value stores with set theory? [closed]

I'm currently developing a simple key-value NoSQL store and want to build its formal model. I'm interested in knowing if there some work about formalization of key-value stores outside of category ...
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1answer
137 views

What are the morphisms of Adj(C,T) - the category whose objects are the adjunctions of a given monad?

The Wikipedia page for Monad says just that for a monad $(T,\eta,\mu)$ we can define the category of all adjunctions that define the monad: Let $\textbf{Adj}(C,T)$ be the category whose objects ...
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2answers
179 views

Category theory and parsers — references wanted

Since I'm interested in parsers (mainly in parser expression grammars), I'm wondering if there's some work that gives a categorical treatment of parsing. Any reference on applications of category ...
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63 views

How to derive a monoid's append from category theory [closed]

As I understand, a monoid $M$ is just a special kind of category; it has only one object and its morphisms can be composed through a composition operation. In principle, if $a$ is the object of the ...
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3answers
332 views

Is there any known CCC closed under a probabilistic powerdomain operation?

Equivalently, is there a known denotational semantics for probabilistic higher-order functional programming languages? Specifically, is there a domain model of pure untyped $\lambda$-calculus extended ...
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3answers
451 views

Uses of $\infty$-categories in TCS

I'm not a theoretical computer scientist. I'm a stable homotopy theorist using $\infty$-categories. I've seen applications of category theory and topos theory to theoretical computer science, and I ...
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0answers
110 views

Distributive law between monads in Haskell

A distributive law between monads must satisfy laws that are usually given in terms of the units $\eta$ and multiplications $\mu$ of the two monads. Among the four laws there are: $\mu^S T \circ S l ...
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3answers
2k views

Impact of Grothendieck's program on TCS

Grothendieck has passed away. He had massive impact on 20th century mathematics continuing into the 21st century. This question is asked somewhat in the style/spirit, for example, of Alan Turing's ...
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2answers
212 views

Are there knot theoretic formulations of NP complete problems?

Are there NP complete(or even NP-hard, or NP) problems that have good topological properties to study. Do NP problems have knot theoretic formulations? We know about #$P$ results about the Jones ...
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1answer
90 views

Relating univalence for a theory of cateogries to the skeleton concept

Say I work in homotopy type theory and my sole objects of study are conventional categories. Equivalences here are given by functors $F:{\bf D}\longrightarrow{\bf C}$ and $G:{\bf ...
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1answer
112 views

Categorical semantics for non-monotonic logics?

Are there any categorical semantics for non-monotonic logics? It appears that the simple answer to this is "No" since the obvious notion of composition fails for any model of a non-monotonic logic. ...
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1answer
124 views

understanding programming monads through diagrams

I am trying to understand better how the category definition of monad is related to the computer science definition. nlab has a rather terse definition of Monad in terms of a bicategory. an object ...
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10answers
4k views

Algebra oriented branch of theoretical computer science

I have a very strong base in algebra, namely commutative algebra, homological algebra, field theory, category theory, and I am currently learning algebraic geometry. I am a math major with an ...
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2answers
239 views

Explaining monad transformers in categorical terms

Most resource regarding categorical notions in programming describe monads, but I've never seen a categorical description of monad transformers. How could monad transformers be described in the terms ...
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158 views

Generalizing Haskell: could we replace Hask with Cat?

N.B. I asked the same question on Stack Overflow but it was suggested that it is too theoretical for this forum. It is great that Haskell allows us to walk around in the category $Hask$. But ...
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3answers
579 views

Categories a computer scientist should know about

I am a computer scientist with a CS degree from the 80's. I am learning category theory by myself. I am looking for advice about learning category theory. E.g. it is quite helpful in learning ...
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2answers
144 views

Isomorphism between algebraic data-types

I have two types of trees in Haskell, defined as the least solution of the following equations: $T_1(A) \cong 1 + A + T_1(A) \times T_1(A)$ $T_2(A) \cong 1 + A \times T_2(A) + T_2(A) \times T_2(A)$ ...
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1answer
133 views

Faithful functors vs forgetful functors: exact category-theoretic defs?

In category theory, a functor between two categories $C,D$ is a map $F$ that assigns to each object (resp. morphism) $x$ of $C$ a corresponding object (resp. morphism) $F(x)$ of $D$ by respecting the ...
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0answers
69 views

Composition series and isogeny

I'm not sure this question is appropriate for this site, but it might have some connections with computational algebra. Consider a fixed "category" $\sf{Cat}$ (in the sense of category theory, but ...
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0answers
129 views

Structures admitting directed sums and directed products?

Some structures have a property of closure by a "sum" or "product" operation. Given a family of structures $(S_i)_{i \in I}$, we can then define a new structure denoted by $\sum_{i \in I} S_i$, resp. ...
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1answer
249 views

Natural Transformations and Parametricity

In Theorems for Free!, Wadler says that the characterization of parametricity can be re-expressed in terms of lax natural transformations and this will be the subject of a further paper. Which paper ...
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Equivalence of categories of directed complete posets

I asked this question there: http://math.stackexchange.com/questions/700975/equivalence-of-categories-of-directed-complete-posets. Since I had no answer, I try here. In the book ``Domains and ...
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1answer
312 views

What's the relation between OOP and category theory?

What's the relation between OOP and category theory? Is there some related work on this topic one can read?
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1answer
192 views

Algebraically Compact Categories

I read Freyd's paper "Algebraically Complete Categories" in the famous Como90 and I have two questions about the notion of algebraic compactness he defined in that paper. (If you are not familiar with ...
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4answers
239 views

What are the uses of Limits and Colimits of Category Theory in every day problems?

I am interested in knowing how we can use the concepts of Limits and Colimits in modeling problems in every day life? Could anyone provide (Software) engineering examples, perhaps? Or describe ...
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1answer
670 views

In what sense are Scala's Try[T] and Future[T] dual?

In a recent course based on Scala I found a hint that the Scala types Try[T] and Future[T] are dual. This was explained only ...
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2answers
594 views

Full Completeness vs Full Abstraction of a program translation

Compiler verification efforts often come down to proving the compiler fully abstract: that it preserves and reflects (contextual) equivalences. Instead of providing full abstraction proofs, some ...
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1answer
225 views

Learning road map for functional programming from the viewpoint of category theory

I am now considering about studying functional programming from the viewpoint of category theory. There are a lot of books about functional programming and category theory, I want some suggestions ...
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1answer
549 views

Hyperdoctrines and Monadic Second Order Logic

This question is essentially the question I asked on Mathoverflow. Monadic Second Order (MSO) logic is second order logic with quantification over unary predicates. That is, quantification over sets. ...
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0answers
191 views

What's the connection between these two categories of games and innocent strategies?

Lately I've been reading a lot about game semantics and in particular the problem of PCF's full abstraction. I'm trying to understand how the definition from this article relates to the one found in ...
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1answer
149 views

Static structure of program

Firstly, I admit that my question is just something very blurred but I hope someone please give me some documents to read. The execution of a program $P$ can be considered as a sequence of state ...
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1answer
288 views

What is the categorical semantics of subtyping?

Starting from Curry-Howard-Lambek, there has been a nice trinity of type theories, logics, and categories. I'm curious what categorical semantics you get when you add (coercive) subtyping to a type ...
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1answer
617 views

What is the difference between arrows and exponential objects in a cartesian closed category?

In a Cartesian Closed Category (CCC), there exist the so-called exponential objects, written $B^A$. When a CCC is considered as a model of the simply-typed $\lambda$-calculus, an exponential object ...
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1answer
190 views

Newbie question: Meta-functions?

Consider a function F that takes a function and produces a function based on structure of the input function. As an example consider F that takes all functions having at least two conditionals and ...
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3answers
853 views

Is there a concept of something like co-applicative functors sitting between comonads and functors?

Any monad is also an applicative functor and any applicative functor is a functor. Also, any comonad is a functor. Is there a similar concept between comonads and functors, something like ...
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1answer
177 views

In what sense are coroutines dual to (sub)routines?

The name coroutine suggests that in some sense they should be dual to (sub)routines. Is there a real mathematical duality? I'm hoping for something like "in category theory subroutines are X and ...
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1answer
641 views

How are Futures described in terms of category theory?

Is there a useful description of futures or promises in terms of category theory? In particular, what could the categorical dual of Future be?
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201 views

Closure ordinals for inductive types with function spaces

Functors built from finite products and sums have closure ordinal $\omega$, detailed nicely in this manuscript by Francois Metayer. i.e. we can reach the inductive type $nat := \mu X. 1 + X$ by ...
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1answer
547 views

A mathematical (categorical) description of type classes

A functional language can be viewed as a category where its objects are types and morphisms functions between them. How do type classes fit in this model? I assume we should only consider those ...
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2answers
2k views

Explaining Applicative functor in categorical terms - monoidal functors

I'd like to understand Applicative in terms of category theory. The documentation for Applicative says that it's a strong lax ...
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1answer
298 views

What can the Haskell package category-extras be used for?

See here. Has anyone attempted to use this to verify category theoretic proofs? Given the relationship between categories and graphs, are there some applications with respect to graph algorithms? What ...
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3answers
2k views

Regular languages from category-theoretical point of view

I noticed that regular languages over the alphabet $\Sigma$ can be naturally thought of as a poset, and indeed a lattice. Moreover, concatenation together with the empty language $\epsilon$ defines a ...
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2answers
240 views

Difference between Stencil -structures and Cellular Automata Category-theoretically?

Definitions Stencil = "For a given point, a stencil is a pre-determined set of nearest neighbors (possibly including itself)." (source) Wikipedia's definition (source) = It ...
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4answers
1k views

Data Structure isomorphisms

Disclaimer: I am not a CS theorist. Coming from abstract algebra, I'm used to dealing with things that are equal up to a isomorphism - but I'm having a trouble translating this concept to data ...
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5answers
383 views

Advantages and specific applications of massively parallel programming thesis idea

I'm nearly graduated in computer science engineering and my thesis should discuss the massively parallel computational model of CUDA and its advantages/applications. I'm searching for an application ...
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2answers
360 views

Is there such a thing as a weak coalgebra homomorphism?

Given an endofunctor $F : Set \rightarrow Set$, we can define observation functions as functions that are polymorphic for any $F$-coalgebra, that is $obs$ is defined for any $F$-coalgebra $\langle A, ...
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319 views

What function has the signature $ A \times \left ( B + C \right ) \rightarrow \left ( A \times B \right ) + \left ( A \times C \right ) $?

$ A \times \left ( B + C \right ) $ is isomorphic to $ \left ( A \times B \right ) + \left ( A \times C \right ) $, right? That means there's a function from one to the other and another function ...
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352 views

Proof theory of biproducts?

A category has biproducts when the same objects are both the products and coproducts. Has anyone investigated the proof theory of categories with biproducts? Perhaps the best-known example is the ...