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Binh Nguyen ngbinh

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Explaining Miles's Magic

Miles Sabin recently opened a pull request fixing the infamous SI-2712. First off, this is remarkable and, if merged, will make everyone's life enormously easier. This is a bug that a lot of people hit often without even realizing it, and they just assume that either they did something wrong or the compiler is broken in some weird way. It is especially common for users of scalaz or cats.

But that's not what I wanted to write about. What I want to write about is the exact semantics of Miles's fix, because it does impose some very specific assumptions about the way that type constructors work, and understanding those assumptions is the key to getting the most of it his fix.

For starters, here is the sort of thing that SI-2712 affects:

def foo[F[_], A](fa: F[A]): String = fa.toString
alexandru /
Last active April 1, 2018 14:57
Task: A diverging design from Future and Scalaz Task
manigandham /
Last active February 3, 2024 22:39
Rich text / HTML editors and frameworks

Strictly Frameworks

Abstracted Editors

These use separate document structures instead of HTML, some are more modular libraries than full editors

OlegIlyenko / Event-stream based GraphQL
Last active February 24, 2024 04:41
Event-stream based GraphQL subscriptions for real-time updates
View Event-stream based GraphQL

In this gist I would like to describe an idea for GraphQL subscriptions. It was inspired by conversations about subscriptions in the GraphQL slack channel and different GH issues, like #89 and #411.

Conceptual Model

At the moment GraphQL allows 2 types of queries:

  • query
  • mutation

Reference implementation also adds the third type: subscription. It does not have any semantics yet, so here I would like to propose one possible semantics interpretation and the reasoning behind it.

cb372 /
Last active May 8, 2023 16:03
Category theory jargon cheat sheet

Category theory jargon cheat sheet

A primer/refresher on the category theory concepts that most commonly crop up in conversations about Scala or FP. (Because it's embarassing when I forget this stuff!)

I'll be assuming Scalaz imports in code samples, and some of the code may be pseudo-Scala.


A functor is something that supports map.

djspiewak /
Created March 22, 2015 19:55
Introduction to scalaz-stream

Introduction to scalaz-stream

Every application ever written can be viewed as some sort of transformation on data. Data can come from different sources, such as a network or a file or user input or the Large Hadron Collider. It can come from many sources all at once to be merged and aggregated in interesting ways, and it can be produced into many different output sinks, such as a network or files or graphical user interfaces. You might produce your output all at once, as a big data dump at the end of the world (right before your program shuts down), or you might produce it more incrementally. Every application fits into this model.

The scalaz-stream project is an attempt to make it easy to construct, test and scale programs that fit within this model (which is to say, everything). It does this by providing an abstraction around a "stream" of data, which is really just this notion of some number of data being sequentially pulled out of some unspecified data source. On top of this abstraction, sca

kchida / gist:d1c15f3968f4f8272c49
Created July 17, 2014 05:06
etcd vs consul vs ???
View gist:d1c15f3968f4f8272c49
- What do Etcd, Consul, and Zookeeper do?
- Service Registration:
- Host, port number, and sometimes authentication credentials, protocols, versions
numbers, and/or environment details.
- Service Discovery:
- Ability for client application to query the central registry to learn of service location.
- Consistent and durable general-purpose K/V store across distributed system.
- Some solutions support this better than others.
- Based on Paxos or some derivative (i.e. Raft) algorithm to quickly converge to a consistent state.
- Centralized locking can be based on this K/V store.

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

So you're curious in learning this new thing called (Functional) Reactive Programming (FRP).

Learning it is hard, even harder by the lack of good material. When I started, I tried looking for tutorials. I found only a handful of practical guides, but they just scratched the surface and never tackled the challenge of building the whole architecture around it. Library documentations often don't help when you're trying to understand some function. I mean, honestly, look at this:

Rx.Observable.prototype.flatMapLatest(selector, [thisArg])

Projects each element of an observable sequence into a new sequence of observable sequences by incorporating the element's index and then transforms an observable sequence of observable sequences into an observable sequence producing values only from the most recent observable sequence.

staltz /
Last active February 28, 2024 15:18
The introduction to Reactive Programming you've been missing
View BasicOperations.scala
object ScalaJSExample extends js.JSApp{
def main() = {
val xs = Seq(1, 2, 3)
val ys = Seq(4, 5, 6)
val zs = for{
x <- xs
y <- ys
} yield x * y