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Composable application architecture with reasonably priced monads

Parleys

15K subscribers • 3 videos on Hallway

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  • Recommended by 1 person: 1 in engineering communities.
  • Presented by Rúnar Bjarnason, co-author of Functional Programming in Scala

Advanced. Deep dive for people who know the field.

11K views10 years ago1 recommendation

Software designProgramming languagesFunctional programmingScalaSoftware architecture

Rúnar Bjarnason explains how to design purely functional application architectures using free monads and free applicatives in Scala.

Most of us have an experience of functional programming that is isolated to small libraries or specific immutable data structures. But can we design our entire application architecture in a purely functional way? Can we do "aspect-oriented" programming with cross-cutting concerns that are compositional and checked by the type system? Yes we can, and in this talk we will look at a conceptually simple recipe for making that happen. We will see that the best things in Scala are Free. Author: Rúnar Bjarnason Rúnar Bjarnason is a senior software developer at Verizon OnCue. Rúnar is co-author of the book "Functional Programming in Scala", and an occasional speaker and blogger on Scala and functional programming.

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1 person recommends this

What people say. Recommended as a classic talk on using free monads for composable functional architecture.

u/PM_ME_UR_OBSIDIANin r/compsci • Recommends

On “Design Patterns for Humans”

IMHO, OOP design patterns lack a punch compared to functional design patterns. Compare and contrast: - The Actor Model for concurrency; - Higher-order combinators for collections (`.map`, `.fold`, `.choose`, `.collect`, ...) which are the ancestor of LINQ; - ~~Monads~~ Burritos; - Applicatives, used for example in `optparse-applicative`; - Free structures as DSLs, particularly free monads and free applicatives; ...and probably many more which I forget right now. These are effective solutions to some very hard problems in software engineering, mostly relating to separation of concerns and testability.
12View on Reddit

u/PM_ME_UR_OBSIDIANin r/compsci • Recommends

On “What extremely simple concept did you first find extremely obscure or plain nonsensical?”

Monads scare people, so let's look into them. A monad is a generic container supporting certain operations. Some examples of monads include lists, optional values, and futures. Here are the required operations: 1. Using a function to independently transform each element in the container into a different element, while preserving the structure of the container. This is called `map`, and can be used like so: `1, 2, 3.map(numberToString) == "one", "two", "three"`. 2. Building an instance of the container from a single value. This is often called `unit`. For the monad to be law-abiding, you need `unit(x).map(f) == unit(f(x))` for any f and x. 3. Flatten nested containers, such that e.g.…
8View on Reddit

u/armandvolkin r/haskell • Mentions

On “Do we need effects to get abstraction?”

It's in Scala, but this talk is what taught me about the coproduct+free approach. Stuff like `freer` & `polysemy` are extensions to this idea.
6View on Reddit

u/armandvolkin r/haskell • Mentions

On “[ANN] polysemy: Higher-order, no-boilerplate, zero-cost free monads”

If you know Scala at all (or maybe even if you don't), I highly recommend Rúnar Bjarnason's "Reasonably Priced Monads" talk from a few years back. afaiu, `polysemy` solves a bunch of less-than-perfect aspects of what is described in that talk (need for boilerplate, performance penalties, inability to express things like `bracket`), but the value proposition is the same.
4View on Reddit

u/fromscalatohaskellin r/scala • Mentions

On “Http4s vs Finch vs Akka-http vs .....?”

…IO monad in haskell, in scala it's usually Task). And we make them happen in very controlled manner. That's how much we care about side effects! You don't have to use monad transformers though (well, kinda... it's good to know as they are useful sometimes even for local computation instead of whole monadT based architecture) - check Free Monads. (link to this video http://degoes.net/articles/modern-fp, http://degoes.net/articles/modern-fp-part-2) >Side-effects are bad when used all over the place, but when a (side)-effect is obvious, such as when making a Http request to another service, it's not hard to understand what's going on. The problem is side-effects where you don't expect them - not side ef…
2View on Reddit

u/refriediin r/scala • Mentions

On “Advice on a good route to Functional Scala”

Take a break from reading to start writing. :-) What are some of your personal FP projects? If you don't have one, you definitely need some! You can even try writing without any dependencies, as an exercise. Unless you need http or sql; don't reimplement http4s or doobie. :-) If you go into withdrawal and do need another talk, check out this one (link to this video by Rúnar of the Red Book if you haven't already.
1View on Reddit