In-house Training Based on CIS 194 Haskell Course
What is this?
We decided we wanted to ramp up the team's functional programming skills. To this end, we committed to working through Brent Yorgey's CIS 194 lecture series on Haskell. This is a 12 week course and there are homework assignments for each week.
Our goal is to work through a week of the course's content every Friday afternoon. Our first session will be on Friday the 20th of July, 2018.
Jump into the #fp channel in the Stacktrace slack to chat about the course, or any FP concepts in general.
How to work with this Repository
Option 1 (recommended)
Install the Nix package manager
Run the following
$ nix-shell --command 'cabal configure --enable-tests && cabal test'
- To run ghci
$ nix-shell --command ghci
From now on you can type
nix-shell and be put into a bash shell which has
hindent. For more info on using Nix ask in #dotfiles.
Install the Haskell Platform. This includes the ghc compiler, ghci repl, and cabal build tool.
Run the following
$ cabal configure $ cabal install cabal-install $ cabal install --only-dependencies --enable-tests $ cabal configure --enable-tests $ cabal test
- To run ghci
You'll be spending a lot of time in
ghci, which is a Read, Eval, Print, Loop (aka 'repl'). Once you enter
ghci you can run commands, which are prefixed with ':'. Entering
:help will print a list of available commands.
The most helpful of these are likely to be
:i for short will tell you everything GHCI can about an expression.
> :i Maybe data Maybe a = Nothing | Just a -- Defined in ‘GHC.Base’ instance Applicative Maybe -- Defined in ‘GHC.Base’ ... MORE > :i (+) class Num a where (+) :: a -> a -> a ... -- Defined in ‘GHC.Num’ infixl 6 +
:t for short will tell you the type of an expression.
> :t Just Just :: a -> Maybe a > :t (+) (+) :: Num a => a -> a -> a
Each week we'll be adding a set of hspec specs in a
./test/Week<N>/ directory. We'll also add some files in
./src/Week<N>/ to serve as a starting point for your implementations. To run only the tests for a given week you can use GHCI. Below is an example of running only the credit card tests for week one.
$ ghci test/Week01/CreditCardValidatorSpec.hs GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /Users/bradparker/code/cosmos/training/CIS194/.ghci Ok, two modules loaded. > hspec spec CreditCardValidator toDigits converts positive Integers to a list of digits FAILED  toDigitsRev does what toDigits does in reverse FAILED  doubleEveryOther doubles every second digit starting from the second last FAILED  sumDigits sums the sum of the digits of all numbers in a list FAILED  validate indicates whether an Integer could be a valid credit card number FAILED  Failures: ... error details and more!
You can also run
dev/watch to get a file-watching test-re-running setup going with the help of GHCID.
To run only the tests for a given spec file using the watch script (defaults to all specs):
$ dev/watch test/Week01/CreditCardValidatorSpec.hs
There is a script
dev/up that will tmux up your editor, tests (using
dev/watch) and a repl for a given week.
tmux-up are provided by
nix so it is best to run it from a
nix-shell detatched from any tmux session(s).
- "windows" | "panes"
- "WeekXX" | "All"
- An editor to run
$ nix-shell $ dev/up windows Week02 vim
$ nix-shell $ dev/up panes All code