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Short (72 chars or less) summary

More detailed explanatory text. Wrap it to 72 characters. The blank
line separating the summary from the body is critical (unless you omit
the body entirely).

Write your commit message in the imperative: "Fix bug" and not "Fixed
bug" or "Fixes bug." This convention matches up with commit messages

vvv

#!/usr/bin/env stack
{- stack --resolver lts-9.21 script
       --package shelly --package text
 -}
{-# OPTIONS_GHC -Wall -Werror #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ExtendedDefaultRules #-}
{-# OPTIONS_GHC -fno-warn-type-defaults #-}

import           Shelly

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#!/usr/bin/env stack
-- stack --resolver lts-9.21 script --package loch-th
{-# LANGUAGE TemplateHaskell #-}
{-# OPTIONS_GHC -Wall -Werror #-}

import Debug.Trace.LocationTH (check)
import System.Environment (getArgs)

main :: IO ()
main = do

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#!/usr/bin/env stack
-- stack --resolver lts-11.2 script
{-# OPTIONS_GHC -Wall -W -Werror #-}

data Foo = Foo
  { fooInt :: Int
  , fooBar :: Bar
  } deriving Show

data Bar = Bar Baz

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{-# OPTIONS_GHC -Wall -Werror #-}

module DaPhone where

import Data.Char (isUpper, toLower)
import Data.List (elemIndex, foldl', intersperse)
import Data.Maybe (catMaybes)

data DaPhone = DaPhone [String]
  deriving (Eq, Show)

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import Data.Foldable (foldl')
import Debug.Trace (trace)

prnEqual :: (Eq a) => a -> a -> IO ()
prnEqual a b = if a == b then print "True" else print "False"

-- Note the absence of parentheses around `Eq a` and having exactly one `print`.
prnEqual' :: Eq a => a -> a -> IO ()
prnEqual' a b = print $ if a == b then "True" else "False"

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{-- XXX Your definition of `checkChar` is okay, but the abstraction itself
 -- is very odd.  It is fine as an exercise of using "do" notation and
 -- `return`. In real code though explicit statements are both short and
 -- expressive (see lines 21-22).
checkChar :: IO Bool
checkChar = do
    c <- getChar
    return (c == 'y')
--}

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listsum :: Num a => [a] -> a
listsum [] = 0
listsum (x:xs) = x + listsum xs

main :: IO ()
main = print $ listsum [1..5]

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{-# LANGUAGE GADTs #-}
module Program where
--
-- The Operational Monad Tutorial:
-- http://apfelmus.nfshost.com/articles/operational-monad.html
--

-- GADT
data Program instr a where
    Then   :: instr a -> (a -> Program instr b) -> Program instr b

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$ cat noexit.sh 
#!/bin/sh
seq 100 | while read; do exit; done  # If `exit' terminated the script ..
echo 'Still alive!'                  # .. this message would not be printed.
$ 
$ sh noexit.sh
Still alive!