her.esy.fun/src/posts/0011-Haskell-Projects/index.org

Create a new Haskell Project

• Haskell Environment Setup
  • Retrieve Compiler
  • Dependency Management
  • Tooling
• Haskell Project directoy structure
  • Tests
  • Benchmarks
  • Profiling
• Haskell Code Architecture
  • Basic: IO
  • Easy: The Handle Pattern
  • Advanced: MTL
  • Expert: Free Monad

Writing a Haskell application can be quite challenging. You must know about:

• setup your coding environment

  • get the right compiler
  • use libraries
  • handle your Haskell tooling, editor/IDE

• project directory structure and best practices

  • write tests
  • benchmarks
  • profiling

• Code architecture

  • encode the data structure
  • manage state and effects

This is both a manual and a tutorial. If you follow it, you should be familiar enough with Haskell to be able to write your own applications. I will focus on command line interfaces and REST APIs.

Haskell Environment Setup

My no brainer solution for it:

1. Write this shell.nix file and launch nix-shell:

   { nixpkgs ? import (fetchGit {
     name = "nixos-release-19.09";
     url = "https://github.com/NixOS/nixpkgs";
     # obtained via
     # git ls-remote https://github.com/nixos/nixpkgs master
     ref = "refs/heads/nixpkgs-19.09-darwin";
     rev = "d5291756487d70bc336e33512a9baf9fa1788faf";
   }) { config = { allowBroken = true; }; } }:
   let
     inherit (nixpkgs) pkgs;
     inherit (pkgs) haskellPackages;
   
     haskellDeps = ps: with ps; [
       base
       protolude
       containers
     ];
   
     hspkgs = haskellPackages;
   
     ghc = hspkgs.ghcWithPackages haskellDeps;
   
     nixPackages = [
       ghc
       pkgs.gdb
       hspkgs.summoner
       hspkgs.summoner-tui
       haskellPackages.cabal-install
       haskellPackages.ghcid
     ];
   in
   pkgs.stdenv.mkDerivation {
     name = "env";
     buildInputs = nixPackages;
     shellHook = ''
           export PS1="\n\[[hs:\033[1;32m\]\W\[\033[0m\]]> "
        '';
   }

1. now launch summon-tui

Retrieve Compiler

Dependency Management

Tooling

Haskell Project directoy structure

Tests

Benchmarks

Profiling

Haskell Code Architecture

Basic: IO

Easy: The Handle Pattern

Advanced: MTL

Expert: Free Monad