Chris A. bitemyapp

Connecting to Redis from Yesod

This is a quick run-through of how I connected to Redis from a Yesod site (which used the default scaffolding). There isn't much specific to Redis here, so this information should apply to connecting to any database or service from Yesod.

Background: Basics of Hedis

First, a brief intro of the basics of Hedis:

{-# LANGUAGE OverloadedStrings #-}

Electric indentation for parentheses, brackets, braces, commas, semicolons...

This isn't an issue of what I want, but rather when I want it. haskell-mode knows how to indent these things correctly, but I had to turn off electric indentation in haskell-mode because it does stupid things the rest of the time.

Concretely, I want a haskell-mode that knows how to be electric when there's only one "right" choice and that doesn't do stupid things when there are multiple possibilities.

	{-# LANGUAGE DeriveFunctor #-}
	{-# LANGUAGE LambdaCase #-}

	import Control.Applicative.Free
	import Control.Monad
	import Control.Monad.Free
	import Control.Monad.Primitive
	import System.Random.MWC.Probability (Prob)
	import qualified System.Random.MWC.Probability as MWC

	module-template: ! 'module MODULE_NAME where

	'
	extensions: {}
	environment: default
	cabal-file: project.cabal
	version: 1
	ghc-args: []
	excluded-modules: []

	-- run it like:
	-- stack ghc --package criterion -- binary.hs -Wall -O2 && ./binary
	{-# LANGUAGE FlexibleInstances #-}
	{-# LANGUAGE BangPatterns #-}
	module Main where

	import Data.ByteString.Lazy (ByteString)
	import Data.Binary
	import Data.Fixed

	{-# language KindSignatures #-}
	{-# language PolyKinds #-}
	{-# language DataKinds #-}
	{-# language TypeFamilies #-}
	{-# language RankNTypes #-}
	{-# language NoImplicitPrelude #-}
	{-# language FlexibleContexts #-}
	{-# language MultiParamTypeClasses #-}
	{-# language GADTs #-}
	{-# language ConstraintKinds #-}

	{-# LANGUAGE LambdaCase #-}
	module Main where

	import Control.Applicative (liftA2)
	import Control.Monad.Reader

	type Varname = String
	type Env = [(Varname, Dom)]

	data Dom

	-- This file is a parsing experiment
	-- Copyright (C) 2015 Fraser Tweedale
	--
	-- This software is free software: you can redistribute it and/or modify
	-- it under the terms of the GNU Affero General Public License as published by
	-- the Free Software Foundation, either version 3 of the License, or
	-- (at your option) any later version.
	--
	-- This program is distributed in the hope that it will be useful,
	-- but WITHOUT ANY WARRANTY; without even the implied warranty of

	// https://twitter.com/bitemyapp/status/672930049830596608

	a[data-nav=moments] {
	display: none !important;
	}

	module Main where

	import qualified System.Directory as Directory
	import qualified System.FilePath as FilePath
	import Control.Monad (forM, forM_, liftM)
	import qualified Data.HashMap.Strict as HashMap
	import Text.Printf (printf)

	isFile :: FilePath -> IO Bool
	isFile = Directory.doesFileExist