Reference. Contextads as Wreaths; Kleisli, Para, and Span Constructions as Wreath Products
We introduce contextads and the Ctx construction, unifying various structures and constructions in category theory dealing with context and contextful arrows – comonads and their Kleisli construction, actegories and their Para construction, adequate triples and their Span construction. Contextads are defined in terms of Lack–Street wreaths, suitably categorified for pseudomonads in a tricategory of spans in a 2-category with display maps. The associated wreath product provides the Ctx construction, and by its universal property we conclude trifunctoriality. This abstract approach lets us work up to structure, and thus swiftly prove that, under very mild assumptions, a contextad equipped colaxly with a 2-algebraic structure produces a similarly structured double category of contextful arrows. We also explore the role contextads might play qua dependently graded comonads in organizing contextful computation in functional programming. We show that many side-effects monads can be dually captured by dependently graded comonads, and gesture towards a general result on the ‘transposability’ of parametric right adjoint monads to dependently graded comonads.
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Cites 70 works (9 here)
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Organizing Physics with Open Energy-Driven Systems capucci-2025-organizing
Profunctor Optics, a Categorical Update clarke-2024-profunctor
Optics are bidirectional data accessors that capture data transformation patterns such as accessing subfields or iterating over containers. Profunctor optics are a particular choice of representation supporting modularity, meaning that we can construct accessors for complex structures by combining simpler ones. Profunctor optics have previously been studied only in an unenriched and non-mixed setting, in which both directions of access are modelled in the same category. However, functional programming languages are arguably better described by enriched categories; and we have found that some structures in the literature are actually mixed optics, with access directions modelled in different categories. Our work generalizes a classic result by Pastro and Street on Tambara theory and uses it to describe mixed V-enriched profunctor optics and to endow them with V-category structure. We provide some original families of optics and derivations, including an elementary one for traversals. Finally, we discuss a Haskell implementation.
Diegetic Representation of Feedback in Open Games capucci-2023-diegetic
Towards Foundations of Categorical Cybernetics capucci-2022-towards
Translating Extensive Form Games to Open Games with Agency capucci-2022-translating
Monoidal Grothendieck construction moeller_vasilakopoulou_2020
We lift the standard equivalence between fibrations and indexed categories to an equivalence between monoidal fibrations and monoidal indexed categories, namely lax monoidal pseudofunctors to the 2-category of categories. Furthermore, we investigate the relation between this ‘global’ monoidal version where the total category is monoidal and the fibration strictly preserves the structure, and a ‘fibrewise’ one where the fibres are monoidal and the reindexing functors strongly preserve the structure, first hinted by Shulman. In particular, when the domain is cocartesian monoidal, we show how lax monoidal structures on a pseudofunctor to Cat bijectively correspond to lifts of the pseudofunctor to MonCat. Finally, we give some examples where this correspondence appears, spanning from the fundamental and family fibrations to network models and systems.
Categorical Logic and Type Theory jacobs-1999
This book is an attempt to give a systematic presentation of both logic and type theory from a categorical perspective, using the unifying concept of fibred category. Its intended audience consists of logicians, type theorists, category theorists and (theoretical) computer scientists.
Two-dimensional monad theory blackwell_kelly_power_1989
Categories for the Working Mathematician maclane_1971
External (61)
- Monoidal Kleisli Bicategories and the Arithmetic Product of Coloured Symmetric Sequences (2024)
- Cartesian double theories: A double-categorical framework for categorical doctrines (2024)
- Topics in low dimensional higher category theory (2024)
- On 2-categorical ∞-cosmoi (2023)
- Two-variable fibrations, factorisation systems and ∞-categories of spans (2023)
- Actegories for the Working Amthematician (2022)
- Categorical Foundations of Gradient-Based Learning (2022)
- Categorical Systems Theory (2022)
- Elements of ∞-Category Theory (2022)
- Dynamic categories, dynamic operads: From deep learning to prediction markets (2022)
- Categorical Foundations of Gradient-Based Learning (2021)
- On the formal theory of pseudomonads and pseudodistributive laws (2021)
- 2-dimensional Categories (2021)
- Double Categories of Open Dynamical Systems (Extended Abstract) (2021)
- Distributive laws, pseudodistributive laws and decagons (2021)
- Backprop as functor: A compositional perspective on supervised learning (2019)
- A 2-Categorical Study of Graded and Indexed Monads (2019)
- Compositional Deep Learning (2019)
- Distributive Laws via Admissibility (2019)
- Cartesian Double Categories with an Emphasis on Characterizing Spans (2018)
- Fibrations and Yoneda's lemma in an ∞-cosmos (2017)
- Towards a formal theory of graded monads (2016)
- Combining effects and coeffects via grading (2016)
- An introduction to multiple categories (On weak and lax multiple categories, I) (2016)
- Enriched categories as a free cocompletion (2016)
- Convex Spaces I: Definition and Examples (2015)
- Polynomials and Models of Type Theory (2015)
- Fusion for free: efficient algebraic effect handlers (2015)
- Parametric effect monads and semantics of effect systems (2014)
- Coherence in three-dimensional category theory (2013)
- Spans in 2-Categories: A monoidal tricategory (2013)
- No-iteration pseudomonads (2013)
- Polynomial functors and polynomial monads (2012)
- Monoidal indeterminates and categories of possible worlds (2012)
- A Unified Framework for Generalized Multicategories (2010)
- A 2-Categories Companion (2010)
- Constructing symmetric monoidal bicategories (2010)
- Comonadic notions of computation (2008)
- Containers: constructing strictly positive types (2005)
- Limits for lax morphisms (2005)
- Proper factorization systems in 2-categories (2003)
- The formal theory of monads II (2002)
- Distributive laws and factorization (2002)
- A coherent approach to pseudomonads (2000)
- Limits in double categories (1999)
- Codata and comonads in Haskell (1999)
- Distributive Laws for Pseudomonads (1999)
- On property-like structures (1997)
- Doctrines whose structure forms a fully faithful adjoint string (1997)
- Higher‐dimensional algebra and topological quantum field theory (1995)
- Monads for which structures are adjoint to units (1995)
- Comprehension categories and the semantics of type dependency (1993)
- Notions of computation and monads (1991)
- Flexible limits for 2-categories (1989)
- Elementary observations on 2-categorical limits (1989)
- Continuity and Effectiveness in Topoi (1986)
- Basic concepts of enriched category theory (1982)
- Tenseurs et machines (1980)
- Fibrations in bicategories (1980)
- Categories of continuous functors, I (1972)
- Strong functors and monoidal monads (1972)