Building something larger requires good software engineering. Building something larger requires good software engineering

Building something larger requires good software engineering.

• Building something larger requires good software engineering.

• Top-down: Start from requirements, then identify the pieces to write, then write the pices.
• Bottom-up: Start building pieces you know, test them, combine them, and keep going until you have your program
• Debugging: Programming is “the art of debugging a blank sheet of paper.”
• Testing: Because nothing complicated and man-made is flawless.
• Maintenance: By far, the most expensive part of any program.

Start from a problem statement. What are you trying to do?

• Start from a problem statement. What are you trying to do?

• Refine the problem statement. Use hierarchical decomposition to define subparts.

• Refine until you know how to write the programs.

• Use procedural abstraction so that higher-level functions are written in terms of lower-level.

Text-based, interactive fiction.

• Text-based, interactive fiction.

• Dates back to 1970's:

• http://en.wikipedia.org/wiki/Colossal_Cave_Adventure

• See Zork at https://youtu.be/1q9Q2gwqw7U

• Play Zork at http://textadventures.co.uk/games/view/5zyoqrsugeopel3ffhz_vq/zork

• There are new and updated tools for making interactive fiction like Inform, http://www.inform-fiction.org

Top-level function:

• Top-level function:

• Tell the user how to play the game.

• Describe the room.

• Get the player's command.

• Figure out the next room.

• Return to Step 2, until the user Quits.

printNow(): Takes a string as input, and prints it on the Command Area immediately.

• printNow(): Takes a string as input, and prints it on the Command Area immediately.

• Print waits until the program is done.

• requestString(): Takes a prompt string as input, accepts a string from the user in a dialog window, then returns the user's input.

How do we keep going, indefinitely, until the user says “quit”?

• How do we keep going, indefinitely, until the user says “quit”?

• A while loop repeats a block until a test becomes false.

def playGame ():

• def playGame ():

• location = "Porch"

• showIntroduction ()

• while not (location == "Exit") :

• showRoom(location)

• direction = requestString("Which direction?")

• location = pickRoom(direction , location)

def showIntroduction ():

• def showIntroduction ():

• printNow("Welcome to the Adventure House!")

• printNow("In each room , you will be told which directions you can go.")

• printNow("You can move north , south , east , or west by typing that direction.")

• printNow("Type help to replay this introduction.")

• printNow("Type quit or exit to end the program.")

def pickRoom(direction , room ):

• def pickRoom(direction , room ):

• if (direction == "quit") or (direction == "exit"):

• printNow("Goodbye!")

• return "Exit"

• if direction == "help":

• showIntroduction ()

• return room

• if room == "Porch":

• if direction == "north":

• return "Entryway"

• if room == "Entryway":

• if direction == "north":

• return "Kitchen"

• if direction == "east":

• return "LivingRoom"

• if direction == "south":

• return "Porch"

• return "LivingRoom"

if room == "Kitchen":

• if room == "Kitchen":

• if direction == "east":

• return "DiningRoom"

• if direction == "south":

• return "Entryway"

• if room == "LivingRoom":

• if direction == "west":

• return "Entryway"

• if direction == "north":

• return "DiningRoom"

• if room == "DiningRoom":

• if direction == "west":

• return "Kitchen"

• if direction == "south":

• return "LivingRoom"

def showPorch():

• def showPorch():

• printNow("You are on the porch of a frightening looking house.")

• printNow("The windows are broken. It's a dark and stormy night.")

• printNow("You can go north into the house. If you dare.")

• def showEntryway():

• printNow("You are in the entry way of the house. There are cobwebs in the corner.")

• printNow("You feel a sense of dread.")

• printNow("There is a passageway to the north and another to the east.")

• printNow("The porch is behind you to the south.")

>>> playGame ()

• >>> playGame ()

• Welcome to the Adventure House!

• In each room , you will be told which directions you

• can go.

• You can move north , south , east , or west by typing that

• direction.

• Type help to replay this introduction.

• Type quit or exit to end the program.

• You are on the porch of a frightening looking house.

Try both expected, and unexpected input.

• Try both expected, and unexpected input.

def pickRoom(direction , room ):

• def pickRoom(direction , room ):

• if (direction == "quit") or (direction == "exit"):

• printNow("Goodbye!")

• return "Exit"

• if direction == "help":

• showIntroduction ()

• return room

• …

• if room == "DiningRoom":

• if direction == "west":

• return "Kitchen"

• if direction == "south":

• return "LivingRoom"

• printNow("You can't (or don't want to) go in that direction.")

• return room #Stay in current room

>>> pickRoom('north ','Porch ')

• >>> pickRoom('north ','Porch ')

• You can't (or don't want to) go in that direction.

• 'Porch '

• >>> pickRoom('Entryway ','Porch ')

• You can't (or don't want to) go in that direction.

• 'Porch '

Learn to trace code

• Learn to trace code

• Print statements are your friends

• Don't be afraid to change the program

• Use comments to “remove” parts temporarily when testing.

When testing, we discover:

• When testing, we discover:

• It's hard to tell which room was which when playing the game.
• We can't figure out what we typed where.

def showRoom(room ):

• def showRoom(room ):

• printNow("===========")

• if room == "Porch":

• showPorch ()

• if room == "Entryway":

• showEntryway ()

• if room == "Kitchen":

• showKitchen ()

• if room == "LivingRoom":

• showLR ()

• if room == "DiningRoom":

• showDR ()

def playGame ():

• def playGame ():

• location = "Porch"

• showIntroduction ()

• while not (location == "Exit") :

• showRoom(location)

• direction = requestString("Which direction?")

• printNow("You typed: "+direction)

• location = pickRoom(direction , location)

Once you make a larger program, you may want to run it in Jython directly.

• Once you make a larger program, you may want to run it in Jython directly.

• Import sys
• Insert the JES sources into your sys.path
• From media import *

• That's it!

Store room descriptions and directions in a list.

• Store room descriptions and directions in a list.

• Easier or harder to change in the future?

• Let each room “remember” (store in a data structure) where the exits and other rooms are.

• Easier or harder to change in the future?

• Let each room be an object that knows how to “show()” and “listExits()”

• Easier or harder to change in the future?

Non-Player Character: Shows up in some rooms, and moves around.

• Non-Player Character: Shows up in some rooms, and moves around.

• Create a ghost variable at the top of the file, before the playGame function.

• ghost = 0

• def playGame():

• location = "Porch"

• showIntroduction()

• while not (location == "Exit") :

• showRoom(location)

• direction = requestString("Which direction?")

• printNow("You typed: "+direction)

• location = pickRoom(direction, location)

def showEntryway():

• def showEntryway():

• global ghost

• printNow("You are in the entry way of the house.")

• printNow(" There are cobwebs in the corner.")

• printNow("You feel a sense of dread.")

• if ghost == 0:

• printNow("You suddenly feel cold.")

• printNow("You look up and see a thick mist.")

• printNow("It seems to be moaning.")

• printNow("Then it disappears.")

• ghost = 1

• printNow("There is a passageway to the north and another to the east.")

• printNow("The porch is behind you to the south.")

def showKitchen():

• def showKitchen():

• global ghost

• printNow("You are in the kitchen. ")

• printNow("All the surfaces are covered with pots,")

• printNow(" pans, food pieces, and pools of blood.")

• printNow("You think you hear something up the stairs")

• printNow(" that go up the west side of the room.")

• printNow("It's a scraping noise, like something being dragged")

• printNow(" along the floor.")

• if ghost == 1:

• printNow("You see the mist you saw earlier.")

• printNow("But now it's darker, and red.")

• printNow("The moan increases in pitch and volume")

• printNow(" so now it sounds more like a yell!")

• printNow("Then it's gone.")

• ghost = 0

• printNow("You can go to the south or east.")