## User login## Navigation |
## Category Theory## Kleisli Arrows of Outrageous FortuneKleisli Arrows of Outrageous Fortune
I discovered this Googling around in an attempt to find some decent introductory material to Kleisli arrows. This isn't introductory, but it's a good resource. :-) The good introductory material I found was this. By Paul Snively at 2011-05-14 15:19 | Category Theory | Functional | Type Theory | 6 comments | other blogs | 15315 reads
## A Lambda Calculus for Real AnalysisA Lambda Calculus for Real Analysis
Paul Taylor is deadly serious about the intersection of logic, mathematics, and computation. I came across this after beating my head against Probability Theory: The Logic of Science and Axiomatic Theory of Economics over the weekend, realizing that my math just wasn't up to the tasks, and doing a Google search for "constructive real analysis." "Real analysis" because it was obvious that that was what both of the aforementioned texts were relying on; "constructive" because I'd really like to develop proofs in Coq/extract working code from them. This paper was on the second page of results. Paul's name was familiar (and not just because I share it with him); he translated Jean-Yves Girard's regrettably out-of-print Proofs and Types to English and maintains a very popular set of tools for typesetting commutative diagrams using LaTeX. By Paul Snively at 2010-02-16 22:00 | Category Theory | Functional | Lambda Calculus | Logic/Declarative | Meta-Programming | Semantics | Type Theory | 9 comments | other blogs | 13919 reads
## Simplicial DatabasesSimplicial Databases, David I. Spivak.
This is what happens when you try to take the existence of ORDER BY and COUNT in SQL seriously. :-) If you're puzzled by how a geometric idea like simplexes could show up here, remember that the algebraic view of simplicial sets is as presheaves on the category of finite total orders and order-preserving maps. Every finite sequence gives rise to a total order on its set of positions, and tables have rows and columns as sequences! ## An Innocent Model of Linear LogicAn Innocent Model of Linear Logic by Paul-André Melliès was referenced by Noam in a serendipitious subthread of the "Claiming Infinities" thread. Here's the abstract:
The introduction goes on to refer to to André Joyal's " Jacques Carette called this paper mind-blowing. My mind-blow warning light already exploded. I'm posting this paper because I know a number of LtUers are interested in these topics, and this way I can buttonhole one of them the next time I see them and ask them to explain it to me. ;) By Anton van Straaten at 2009-12-18 03:23 | Category Theory | 8 comments | other blogs | 12673 reads
## Lawvere Theories and MonadsMartin Hyland and John Power (2007). The Category Theoretic Understanding of Universal Algebra: Lawvere Theories and Monads. ENTCS 172:437-458. Both monads and Lawvere theories provide characterisations of algebraic structure, with monads providing the more general characterisation. The authors provide an introduction to Lawvere theories, discusses their relationship to sets, and why monads became the more popular treatment. Then they tackle the application of the theory to the semantics of side effects, where they argue that the generality of monads allow them to characterise computational phenomena that are not to do with side effects such as partiality and continuations, and argue that Lawvere theories more cleanly characterise what side effects are. This paper is a good introduction to an important line of recent research done by Hyland&Power; cf. also the LtU story Combining computational effects. ## Parameterized Notions of ComputationParameterized Notions of Computation, Robert Atkey, JFP 2008.
Once you've programmed with monads for a while, it's pretty common to start defining parameterized families of monads -- e.g., we might define a family of type constructors for IO, in which the program type additionally tracks which files the computation reads and writes from. This is a very convenient programming pattern, but the theory of it is honestly a little sketchy: on what basis do we conclude that the indices we define The application to delimited continuations is quite nice, and the type theories can also give a little insight into the basics of how stuff like Hoare Type Theory works (which uses parameterized monads, with a very sophisticated language of parameters). On a slightly tangential note, this also raises in my mind a methodological point. Over the last By neelk at 2009-02-11 21:40 | Category Theory | Lambda Calculus | Semantics | Type Theory | 16 comments | other blogs | 13661 reads
## Computation and the Periodic TableBy now there is an extensive network of interlocking analogies between physics, topology, logic and computer science, which can be seen most easily by comparing the roles that symmetric monoidal closed categories play in each subject. However, symmetric monoidal categories are just the n = 1, k = 3 entry of a hypothesized â€œperiodic tableâ€ of k-tuply monoidal n-categories. This raises the question of how these analogies extend. We present some thoughts on this question, focusing on how monoidal closed 2-categories might let us understand the lambda calculus more deeply. ## Arrows generalise monads and idioms
Two fresh papers from the Edinburgh theory stable:
- Lindley, Wadler & Yallop, 2008. The Arrow Calculus, (Functional Pearl) (submitted to ICFP).
- Lindley, Wadler & Yallop, 2008. Idioms are oblivious, arrows are meticulous, monads are promiscuous (submitted to MSFP)
We revisit the connection between three notions of computation: Moggiâ€™s monads, Hughesâ€™s arrows and McBride and Patersonâ€™s idioms (also called applicative functors ). We show that idioms are equivalent to arrows that satisfy the type isomorphism A ∼> B ≅ 1 ∼> (A -> B) and that monads are equivalent to arrows that satisfy the type isomorphism A ∼> B ≅A â†’ (1 ∼> B). Further, idioms embed into arrows and arrows embed into monads.
## Species: making analytic functors practical for functional programmingSpecies: making analytic functors practical for functional programming, Jacques Carette and Gordon Uszkay. Submitted to MSFP 2008.
Learning more about the theory of species and working out its implications for programming has been on my to-do list for several years now. It really seems like the natural way to more tightly integrate combinatoric ideas into the functional programming style. (For an example of how fruitful this connection can be, consider how datatype differentiation explains zippers/functional pointers.) However, there's been this whole "graduation" and "primary research focus" stuff that's kept getting in the way, so I'm happy to see that Carette and Uszkay are figuring it out so I can just crib from them. :) ## Help John Baez and Mike Stay!John Baez and Mike Stay are working on a book chapter titled "Categories in Physics, Topology, Logic and Computation: a Rosetta Stone." They previously asked for some help with the logic section, and now they're looking for help with the computation section:
This is already a great introductory paper, but the computation section is indeed quite rough. Obviously comments are welcome, but even if you don't have anything to add, the first sections are sure to be enjoyable for many LtU readers. The paper does not assume any background in category theory, logic or physics and manages to be an excellent introduction to the surprising connections between these fields. If you have some background, it's a very quick and fun read, and if you can offer feedback, so much the better! |
## Browse archives
## Active forum topics## New forum topics |

## Recent comments

4 days 22 hours ago

2 weeks 3 days ago

2 weeks 6 days ago

3 weeks 6 days ago

4 weeks 3 days ago

4 weeks 3 days ago

4 weeks 3 days ago

6 weeks 17 hours ago

6 weeks 17 hours ago

7 weeks 6 days ago