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

friedbrice

-- monadstate-example.hs
--
-- Load this program in GHCi:
--
--     stack repl \
--         --resolver nightly \
--         --package transformers \
--         --package mtl \
--         monadstate-example.hs
--

friedbrice

-- ghcid -c'stack repl --resolver nightly --package time' haskell-time.hs --allow-eval

----
-- # Haskell Time Crib Sheet
----

-- Excellent sources for this small guide include:
--
--   * https://two-wrongs.com/haskell-time-library-tutorial.html
--   * https://williamyaoh.com/posts/2019-09-16-time-cheatsheet.html

friedbrice

var danielsLensTalk = {
    recordId: 0,
    creation: {
        user: 'danielbrice@gmail.com',
        moment: {
            date: {
                year: 2019,
                month: 5,
                day: 29
            },

nrinaudo

Introduction

I was recently asked to explain why I felt disappointed by Haskell, as a language. And, well. Crucified for crucified, I might as well criticise Haskell publicly.

First though, I need to make it explicit that I claim no particular skill with the language - I will in fact vehemently (and convincingly!) argue that I'm a terrible Haskell programmer. And what I'm about to explain is not meant as The Truth, but my current understanding, potentially flawed, incomplete, or flat out incorrect. I welcome any attempt at proving me wrong, because when I dislike something that so many clever people worship, it's usually because I missed an important detail.

Another important point is that this is not meant to convey the idea that Haskell is a bad language. I do feel, however, that the vocal, and sometimes aggressive, reverence in which it's held might lead people to have unreasonable expectations. It certainly was my case, and the reason I'm writing this.

Type classes

I love the concept of type class

chrisdone

Statically checked overloaded strings

This gist demonstrates a trick I came up with which is defining IsString for Q (TExp a), where a is lift-able. This allows you to write $$("...") and have the string parsed at compile-time.

On GHC 9, you are able to write $$"..." instead.

This offers a light-weight way to enforce compile-time constraints. It's basically OverloadedStrings with static checks. The inferred return type

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:

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 #-}