laiboonh/haskell

Learning Haskell

Setting up GHCI via stack

1. Install haskell tool stack
2. stack setup
3. stack ghci

Setting up Atom

1. search for package atom-beautify language-haskell linter linter-hlint
2. stack install stylish-haskell

Using GHCI

1. To import modules :m +Data.List
2. To undo import modules :m -Data.List
3. To load :l workspace.hs
4. To reload :r
5. To find out more info :i (++)
6. To find out type :t (++)
7. To key in a block of codes :{ :}

λ> :{
Prelude| k (x,y) = x
Prelude| :}
k :: (t, t1) -> t

8. To browse functions in a module :browse! Data.Maybe

λ> :browse! Data.Maybe
-- not currently imported
Data.Maybe.catMaybes :: [Maybe a] -> [a]
Data.Maybe.fromJust :: Maybe a -> a
Data.Maybe.fromMaybe :: a -> Maybe a -> a
Data.Maybe.isJust :: Maybe a -> Bool
Data.Maybe.isNothing :: Maybe a -> Bool
Data.Maybe.listToMaybe :: [a] -> Maybe a
Data.Maybe.mapMaybe :: (a -> Maybe b) -> [a] -> [b]
Data.Maybe.maybeToList :: Maybe a -> [a]
-- imported via Prelude
maybe :: b -> (a -> b) -> Maybe a -> b
Just :: a -> Maybe a
data Maybe a = Nothing | Just a
Nothing :: Maybe a

Customize GHCI

Edit appropriate ghci.conf file.

In Windows : C:\Users\lbh\AppData\Roaming\ghc\ghci.conf

In Mac : /Users/lbh/.ghc/ghci.conf

1. Set ghci to accept multiline input
2. Change the prompt
3. Show type after evaluation
4. Set macro for displaying present working Directory
5. Set macro for git add all
6. Set macro for git commit all with message
7. Set macro for git push

:set +m
:set prompt "\x03BB> "
:set +t
:def pwd (\_-> System.Directory.getCurrentDirectory >>= print >> return "")
:def gitA (\_ -> System.Process.rawSystem "git" ["add", "-A"] >>= print >> return "")
:def gitC (\m -> System.Process.rawSystem "git" ["commit", "-am", m] >>= print >> return "")
:def gitP (\_ -> System.Process.rawSystem "git" ["push"] >>= print >> return "")

Changing directory within GHCI

--because of macro set in earlier step
λ> :pwd
"C:\\Users\\lbh"
λ> :cd haskell\\
λ> :pwd
"C:\\Users\\lbh\\haskell"

Compiling haskell code

1. stack ghc -- Main.hs -o simple generates the interface file .hi and object file .o as well as linking the executable "simple"
2. If your source file has dependencies on other object files they will be linked automatically assuming they are in the same directory

Compiling modular haskell files

1. Assuming you have a Listy.hs and a ListIntances.hs depends on it
2. stack ghc -- ListyInstances.hs -I. --make We include the current directory and make modules within it discoverable

Cabal init

1. cabal init --help
2. cabal init -n -l BSD3 --is-executable --language=Haskell2010 -a 'laiboonh' -s 'Saying Hello' -p hello-haskell
3. cabal sandbox init To isolate dependencies to this project, if not dependencies will be installed into package-db in home directory
4. cabal install --only-dependencies To install dependencies
5. cabal build
6. ./dist/build/hello-haskell/hello-haskell
7. cabal repl

Including a locally developed library

1. cabal sandbox init
2. cabal sandbox add-source ../hello-haskell
3. cabal install --only-dependencies

Including Test suite in Cabal

1. cabal configure --enable-tests