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@taktoa
taktoa / haskell-pain-points.md
Last active October 26, 2019 04:18
A rant about pain points in Haskell, written as a response to https://redd.it/7rwuxb

I started writing this polemic to answer your question, but I ended up touching on most of my gripes with Haskell in general, not just in a corporate context.

GHC

GHC is a modern compiler with an amazing RTS and tons of features, but I have some issues with it.

Monolithic and Hard to Contribute To

@pchiusano
pchiusano / Interpreters.scala
Created September 21, 2017 20:51
Code for Scala World 2017 talk on eliminating interpreter overhead via partial evaluation
package scalaworld.interpreters
/*
This file shows a simple language, an interpreter, and two
partial evaluators for that language, along with a profiling suite.
*/
trait Expr // denotes a Vector[Double] => Vector[Double]
object Expr {
@SystemFw
SystemFw / Free conversation.md
Last active October 17, 2023 09:57
Explaining some of the mechanics of interpretation of Free programs

Balaji Sivaraman @balajisivaraman_twitter

Hi all, I need some help understanding a piece of Doobie code from the examples. It is the StreamingCopy one: (https://github.com/tpolecat/doobie/blob/series/0.4.x/yax/example/src/main/scala/example/StreamingCopy.scala). I am using a modified version of the fuseMap2 example from that file. Here’s how I’ve modified it for my requirements:

  def fuseMap[F[_]: Catchable: Monad, A, B](
      source: Process[ConnectionIO, A],
      sink: Vector[A] => ConnectionIO[B],
      delete: ConnectionIO[Unit]
  )(
 sourceXA: Transactor[F],
@taktoa
taktoa / incremental.nix
Last active January 8, 2018 12:57
Build the profunctors library incrementally using Nix.
with builtins;
rec {
pkgs = import <nixpkgs> {};
testGHC = pkgs.haskellPackages.ghcWithPackages (p: with p; [
base base-orphans bifunctors comonad contravariant distributive
tagged transformers
]);
@tonymorris
tonymorris / free-classy-prisms.hs
Created April 28, 2017 07:35
Free monad with classy prisms on grammar
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE DeriveFunctor #-}
import Control.Lens
import Prelude hiding (readFile, writeFile, print)
import qualified Prelude as Prelude(readFile, writeFile, print)
@non
non / laws.md
Last active February 20, 2022 00:26
I feel like conversations around laws and lawfulness in Scala are often not productive, due to a lack of rigor involved. I wanted to try to be as clear and specific as possible about my views of lawful (and unlawful) behavior, and what I consider a correct and rigorous way to think about laws (and their limits) in Scala.

Laws

A law is a group of two or more expressions which are required to be the same. The expressions will usually involve one or more typed holes ("inputs") which vary.

Some examples:

x.map(id) === x
@pchiusano
pchiusano / traverse.scala
Created March 23, 2017 15:02
Another encoding of `Traverse` in terms of `mapAccumulate`
/**
* In this version of `Traverse`, sequencing always goes through `List` (or some other canonical sequence type),
* which can be done in a stack-safe manner using a balanced fold as in https://gist.github.com/pchiusano/7667597.
* It's quite nice that `sequence` and `traverse` are now derived functions.
*/
trait Traverse[F[_]] extends Functor[F] {
/** Inefficient but correct implementation of `toList` in terms of `mapAccumulate`. */
def toList[A](f: F[A]): List[A] = mapAccumulate(f, List())((a, rbuf) => (a, a :: rbuf))._2.reverse
/** The only function that must be implemented. Must be consistent with `map`. */
@paulp
paulp / global.sbt
Last active October 16, 2018 19:09
continuous compilation of the sbt build
// These lines go in ~/.sbt/0.13/global.sbt
watchSources ++= (
(baseDirectory.value * "*.sbt").get
++ (baseDirectory.value / "project" * "*.scala").get
++ (baseDirectory.value / "project" * "*.sbt").get
)
addCommandAlias("rtu", "; reload ; test:update")
addCommandAlias("rtc", "; reload ; test:compile")
addCommandAlias("ru", "; reload ; update")
@chadselph
chadselph / AkkaHttpHeaderExtractor.scala
Last active July 3, 2022 16:04
akka-http directive for opentracing.io
import java.util
import java.util.Map.Entry
import akka.http.scaladsl.model.HttpHeader
import io.opentracing.propagation.TextMap
import scala.collection.JavaConverters.asJavaIteratorConverter
/**
* Used to extract an iterator of Entry[String, String] to the
@aherrmann
aherrmann / pnix-shell.sh
Last active August 23, 2020 20:31
Fully persistent Nix shell
# This is free and unencumbered software released into the public domain.
# Anyone is free to copy, modify, publish, use, compile, sell, or
# distribute this software, either in source code form or as a compiled
# binary, for any purpose, commercial or non-commercial, and by any
# means.
# In jurisdictions that recognize copyright laws, the author or authors
# of this software dedicate any and all copyright interest in the
# software to the public domain. We make this dedication for the benefit