Source code from Episode 003 of the_dev_aspect

003_1_initial_code.fs

//
// --------- Model ---------
//

type Details =
    { Name: string
      Description: string }

type Item =
    { Details: Details }

type RoomId =
    | RoomId of string

type Exit =
    | PassableExit of string * destination: RoomId
    | LockedExit of string * key: Item * next: Exit 
    | NoExit of string option

type Exits =
    { North: Exit
      South: Exit
      East: Exit
      West: Exit }

type Room =
    { Id: RoomId
      Details: Details
      Items: Item list
      Exits: Exits }

type Player =
    { Details: Details
      Location: RoomId
      Inventory: Item list }

type World =
    { Rooms: Map<RoomId, Room> 
      Player: Player }

// --------- Initial World ---------

let key: Item = 
    { Details =
          { Name = "A shiny key"
            Description = "This key looks like it could open a nearby door."} }

let allRooms = [
    
    { Id = RoomId "center"
      Details = 
          { Name = "A central room"
            Description = "You are standing in a central room with exits in all directions.  A single brazier lights the room."}
      Items = []
      Exits =
          { North = PassableExit ("You see a darkened passageway to the north.", RoomId "north1")
            South = PassableExit ("You see door to the south.  A waft of cold air hits your face.", RoomId "south1")
            East = LockedExit ("You see a locked door to the east.", key, PassableExit ("You see an open door to the east.", RoomId "east1"))
            West = PassableExit ("You see an interesting room to the west.", RoomId "west1") }}

    { Id = RoomId "north1"
      Details = 
          { Name = "A dark room"
            Description = "You are standing in a very dark room.  You hear the faint sound of rats scurrying along the floor."}
      Items = []
      Exits =
          { North = NoExit None
            South = PassableExit ("You see an dimly lit room to the south.", RoomId "center")
            East = NoExit None
            West = NoExit None }}

    { Id = RoomId "south1"
      Details = 
          { Name = "A cold room"
            Description = "You are standing in a room that feels very cold.  Your breath instantly turns into a white puff."}
      Items = []
      Exits =
          { North = PassableExit ("You see an exit to the north.  That room looks much warmer.", RoomId "center")
            South = NoExit None
            East = NoExit None
            West = NoExit None }}

    { Id = RoomId "west1"
      Details = 
          { Name = "A cozy room"
            Description = "This room seems very cozy, as if someone had made a home here.  Various personal belongings are strewn about."}
      Items = [ key ]
      Exits =
          { North = NoExit None
            South = NoExit None
            East = PassableExit ("You see a doorway back to the lit room.", RoomId "center")
            West = NoExit None }}

    { Id = RoomId "east1"
      Details = 
          { Name = "An open meadow"
            Description = "You are in an open meadow.  The sun is bright and it takes some time for your eyes to adjust."}
      Items = []
      Exits =
          { North = NoExit None
            South = NoExit None
            East = NoExit None
            West = PassableExit ("You see stone doorway to the west.  Why would you want to go back there?", RoomId "center") }}
]

let player =
    { Details = { Name = "Luke"; Description = "Just your average adventurer."}
      Inventory = []
      Location = RoomId "center" }

let gameWorld =
    { Rooms =
        allRooms
        |> Seq.map (fun room -> (room.Id, room))
        |> Map.ofSeq
      Player = player}

//
// --------- Logic --------- 
//

003_2_final_code.fs

//
// --------- Model ---------
//

type Details =
    { Name: string
      Description: string }

type Item =
    { Details: Details }

type RoomId =
    | RoomId of string

type Exit =
    | PassableExit of string * destination: RoomId
    | LockedExit of string * key: Item * next: Exit 
    | NoExit of string option

type Exits =
    { North: Exit
      South: Exit
      East: Exit
      West: Exit }

type Room =
    { Id: RoomId
      Details: Details
      Items: Item list
      Exits: Exits }

type Player =
    { Details: Details
      Location: RoomId
      Inventory: Item list }

type World =
    { Rooms: Map<RoomId, Room> 
      Player: Player }

// --------- Initial World ---------

let key: Item = 
    { Details =
          { Name = "A shiny key"
            Description = "This key looks like it could open a nearby door."} }

let allRooms = [
    
    { Id = RoomId "center"
      Details = 
          { Name = "A central room"
            Description = "You are standing in a central room with exits in all directions.  A single brazier lights the room."}
      Items = []
      Exits =
          { North = PassableExit ("You see a darkened passageway to the north.", RoomId "north1")
            South = PassableExit ("You see door to the south.  A waft of cold air hits your face.", RoomId "south1")
            East = LockedExit ("You see a locked door to the east.", key, PassableExit ("You see an open door to the east.", RoomId "east1"))
            West = PassableExit ("You see an interesting room to the west.", RoomId "west1") }}

    { Id = RoomId "north1"
      Details = 
          { Name = "A dark room"
            Description = "You are standing in a very dark room.  You hear the faint sound of rats scurrying along the floor."}
      Items = []
      Exits =
          { North = NoExit None
            South = PassableExit ("You see an dimly lit room to the south.", RoomId "center")
            East = NoExit None
            West = NoExit None }}

    { Id = RoomId "south1"
      Details = 
          { Name = "A cold room"
            Description = "You are standing in a room that feels very cold.  Your breath instantly turns into a white puff."}
      Items = []
      Exits =
          { North = PassableExit ("You see an exit to the north.  That room looks much warmer.", RoomId "center")
            South = NoExit None
            East = NoExit None
            West = NoExit None }}

    { Id = RoomId "west1"
      Details = 
          { Name = "A cozy room"
            Description = "This room seems very cozy, as if someone had made a home here.  Various personal belongings are strewn about."}
      Items = [ key ]
      Exits =
          { North = NoExit None
            South = NoExit None
            East = PassableExit ("You see a doorway back to the lit room.", RoomId "center")
            West = NoExit None }}

    { Id = RoomId "east1"
      Details = 
          { Name = "An open meadow"
            Description = "You are in an open meadow.  The sun is bright and it takes some time for your eyes to adjust."}
      Items = []
      Exits =
          { North = NoExit None
            South = NoExit None
            East = NoExit None
            West = PassableExit ("You see stone doorway to the west.  Why would you want to go back there?", RoomId "center") }}
]

let player =
    { Details = { Name = "Luke"; Description = "Just your average adventurer."}
      Inventory = []
      Location = RoomId "center" }

let gameWorld =
    { Rooms =
        allRooms
        |> Seq.map (fun room -> (room.Id, room))
        |> Map.ofSeq
      Player = player}

//
// --------- Logic --------- 
//

type Result<'TSuccess, 'TFailure> =
    | Success of 'TSuccess
    | Failure of 'TFailure

let bind processFunc lastResult =
    match lastResult with
    | Success s -> processFunc s
    | Failure f -> Failure f

let (>>=) x f =
    bind f x

let switch processFunc input =
    Success (processFunc input)

let getRoom world roomId =
    match world.Rooms.TryFind roomId with
    | Some room -> Success room
    | None -> Failure "Room does not exist!"

let describeDetails details =
    sprintf "\n\n%s\n\n%s\n\n" details.Name details.Description

let extractDetailsFromRoom (room: Room) =
    room.Details

let describeCurrentRoom world =
    world.Player.Location
    |> getRoom world
    |> (bind (switch extractDetailsFromRoom) >> bind (switch describeDetails))

let north ({ North = northExit }: Exits) = northExit
let south ({ South = southExit }: Exits) = southExit
let east ({ East = eastExit }: Exits) = eastExit
let west ({ West = westExit }: Exits) = westExit

let getCurrentRoom world =
    world.Player.Location
    |> getRoom world

let setCurrentRoom world room =
    { world with
        Player = { world.Player with Location = room.Id} }

let getExit direction exits =
    match (direction exits) with
    | PassableExit (_, roomId) -> Success roomId
    | LockedExit (_, _, _) -> Failure "There is a locked door in that direction."
    | NoExit (_) -> Failure "There is no room in that direction."

let move direction world =
    world
    |> getCurrentRoom
    >>= switch (fun room -> room.Exits) 
    >>= getExit direction
    >>= getRoom world
    >>= switch (setCurrentRoom world)

let displayResult result =
    match result with
    | Success s -> printf "%s" s
    | Failure f -> printf "%s" f

gameWorld
|> move south
|> bind (move north)
|> bind (move east)
|> bind describeCurrentRoom
|> displayResult