paulkoerbitz

data Lit = Lit Int
data Add l r = Add l r

class Eval x where
  eval :: x -> Int

instance Eval Lit where
  eval (Lit x) = x

instance (Eval l, Eval r) => Eval (Add l r) where

jessitron

Letter to a Young Haskell Enthusiast, by Gershom Bazerman.

Condensed from: http://comonad.com/reader/2014/letter-to-a-young-haskell-enthusiast/

The following letter is about tendencies that come with the flush of excitement of learning any new thing. It is written specifically, because if we don't talk specifics, the generalities make no sense. It is a letter full of things I want to remember.

You’ve entered the world of strongly typed functional programming, and it is great. You want to share the great things you’ve learned, and you want to slay all the false statements in the world.

StevenClontz

require 'csv'
require 'pry'
require 'erb'

class Student
  attr_reader :id, :name, :section
  attr_accessor :group1,
                :group2,
                :absences,
                :diagnostic,

androidfred

Haskell, Stack and Intellij IDEA IDE setup tutorial how to get started

Upon completion you will have a sane, productive Haskell environment adhering to best practices.

Basics

• Haskell is a programming language.
• Stack is tool for Haskell projects. (similar tools for other languages include Maven, Gradle, npm, RubyGems etc)
• Intellij IDEA IDE is a popular IDE.

Install required libraries

sudo apt-get install libtinfo-dev libghc-zlib-dev libghc-zlib-bindings-dev

chrisdone

Introducing the stack hoogle feature!

With the release of hoogle5, we can now hoogle all local packages.

This let us implement stack hoogle, which is on the master branch of stack, but is not yet on a stack release. We'd like you to try it out before we do!

To upgrade to the latest stack from git, use:

PkmX

{-# LANGUAGE GADTs #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE OverloadedLabels #-}

mtesseract

The Problem

Defining records in Haskell causes accessor functions for the record's fields to be defined. There is no seperate namespace for these accessor functions.

The Goal

Be able to

• use records in Haskell, which share field names.
• use lenses for accessing these fields

lspitzner

my sublime setup for haskell includes:

• SublimeHaskell, but with most features disabled. mostly for syntax highlighting. (as was pointed out, it is sufficient to grab the *theme file and omit the rest of the plugin. And even that is optional.)
• for auto-formatting:
  • this (slightly modified) external-command plugin: https://github.com/lspitzner/SublimeExternalCommand
  • brittany (installed so that is on path)
  • the below keybind (you can open the user keybindings in sublime and merge the below)
  • you can either select some function and reformat that by pressing f9, or select nothing (whole file gets formatted)
• for quick compilation feedback:

fsestini

{-# LANGUAGE TemplateHaskell, RankNTypes #-}

module DbCodeGen where

import Data.List (intercalate)
import Control.Lens

type Endo a = a -> a
fix :: Endo a -> a
fix f = f (fix f)

i-am-tom

{-# LANGUAGE AllowAmbiguousTypes    #-}
{-# LANGUAGE DataKinds              #-}
{-# LANGUAGE DeriveGeneric          #-}
{-# LANGUAGE FlexibleContexts       #-}
{-# LANGUAGE FlexibleInstances      #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE PolyKinds              #-}
{-# LANGUAGE ScopedTypeVariables    #-}
{-# LANGUAGE TypeApplications       #-}
{-# LANGUAGE TypeFamilies           #-}