Quick peek at some places in code

Main.hs has our Main module definition. It was generated by Stack when we started. In the end of the main function, it calls run function, which is defined in Run.hs file. This is the place where we can see overall flow of the program in one glance.

run :: RIO App ()

run = do

choice <- showMainMenu

case choice of

StarNewGame -> do

logDebug "New game starting..."

logDebug "Rolling new character..."

player <- liftIO $ evalRandIO rollNewCharacter

displayNewCharacter player

logDebug "Selecting starting gear..."

gear <- selectStartingGear $ playerGear player

logDebug "Preparing game..."

game <- liftIO $ evalRandIO $ startGame player gear

logDebug "Dealing first card..."

finishedGame <- playGame game

logDebug "Displaying game over..."

displayGameOver finishedGame

ExitGame ->

return ()

Another interesting module is Types. Here you can find how player, items, monsters and such are represented.

Third and biggest module is UserInterface, which contains functions to display game status to player and ask their input.

So, what does our run function do? Lets have a look:

choice <- showMainMenu

show main menu and ask for player input

case choice of

depending on the choice, continue with game logic or exit the function

player <- liftIO $ evalRandIO rollNewCharacter

roll a new character

evalRandIO indicates we're dealing with random numbers

displayNewCharacter player

display the new character on screen

gear <- selectStartingGear $ playerGear player

select starting gear

game <- liftIO $ evalRandIO $ startGame player gear

shuffle the deck and set up the game

again using random numbers here

finishedGame <- playGame game

play game until we're done

displayGameOver finishedGame

display game over screen

Word about input and output

One of the features of Haskell I like is the ability to show which functions are pure (always returning same output with given set of inputs and not having any side effects). In our program, every function that returns RIO a b has access to input and output. In addition to that, it also has access to system wide configuration (which we don't use much here) and logging functions.

To write on the screen, we use putStrLn and reading a user input readLine. Since they're designed to work with IO instead of RIO a b, we have to use liftIO. But all that is technical details that we won't worry now.

App is our configuration. We aren't directly using it, so it's safe to ignore for now.

Showing main menu

showMainMenu function will print out the menu and then call mainMenuInput. mainMenuInput will read input, validate that it's either 1 or 2 and return respectively StarNewGame or ExitGame. In case user enters something else, mainMenuInput will recurse until user enters valid input.

-- | Display main menu

showMainMenu :: RIO App MainMenuChoice

showMainMenu = do

logDebug "Displaying main menu"

liftIO $ putStrLn "nn