T ask O riented P rogramming i n using Rinus Plasmeijer – Bas Lijnse - Peter Achten

1. Task Oriented Programming in using Rinus Plasmeijer–Bas Lijnse- Peter Achten Pieter Koopman- Steffen Michels-JurriënStutterheim Jan Martin Jansen (NLDA) - Laszlo Domoszlai (ELTE) ASSIGNMENTS Radboud University Nijmegen

2. 1. Getting started • Start the CleanIDE and open (‘File:Open… (Ctrl+O)’) the project at:iTasks-SDK/Examples/BasicAPIExamples.prj • Create and launch (‘Project:Update and Run (Ctrl+R)’) the server application • Open your favorite web browser and navigate to: http://localhost/  • Log in anonymously by pressing the ‘Continue’ button giving   

3. 2. Tasks panel • Determine the relation between the tasks panel  and the definition of the function basicAPIExamples in the main module BasicAPIExamples.icl 

4. 3. Persistent tasks • Start  ‘Interaction with basic types’ tasks from the tasks panel • The work view panel  displays the tasks assigned to you • The task view panel  displays the current state of these tasks • In the task view panel, manipulate tasks • At any stage, close  a task in the task view panel and reopen it      

5. 4. Custom types • Study the relationship between the type of the task ‘Enter a person’ and the rendered interactive task • Do the same for the ‘Enter multiple persons’ task • Add a task named viewPerson to ‘Interaction with custom types’ that merely views a person using viewInformation with an empty list ([ ]) of ViewOption-s.

6. 5. Customized view • In the task viewPerson, add a ViewOption element that limits the view to the current name and gender of the person. What is the effect of this change? • In the task enterPerson, add an EnterOption element that limits entering information to a name and gender only. The dateOfBirth field is always set to Nothing. What is the effect of this change? • Tips: • in the CleanIDE you can quickly find the definition of a function or type as follows: • double-click the identifier while holding Ctrl selects the definition • double-click the identifier while holding Ctrl+Altselects the implementation • in the CleanIDEthe command 'Help:Help:UserManual.pdf' opens the user manual of the CleanIDE. Appendix A and B summarize the standard key mappings and shortkeys

7. Intermezzo • At: https://wiki.clean.cs.ru.nl/ITasks#Snapshot_for_CEFP_2013_Course, download Ligretto_framework.zip • Unzip it in the same directory as BasicAPIExamples. This adds the following modules: • ligretto.dcl and ligretto.icl: a fairly complete logic model for the Ligretto case study • ligrettoTOP.dcland ligrettoTOP.icl:an incomplete start-up module in which you can create your cool version of Ligretto • In module BasicAPIExamples.icladd the following line: • import ligrettoTOP • and in function basicAPIExamplesadd an entry to play Ligretto: • ,workflow "Ligretto" "Play Ligretto"play_ligretto • Tip: • any task can be easily tested by adding it to the function basicAPIExamplesin the same way as done above for the task play_ligretto

8. 6. Play with HTML • In module ligrettoTOP.icl you find functions that render a single card (view_card), the row of a player (view_row), and the ligretto pile (view_ligretto). Study these functions. • Create in a similar way the function view_hand :: Hand -> HtmlTag that displays the back side of the card on top of the conceal pile and the front side of the card on top of the discard pile. • Tip: • if you find the definition of type HtmlTagthen you will see that it is a Clean data representation of standard html-tags. With these tags you can insert your own html if necessary.

9. 7. Viewing a Player • Extend module ligrettoTOP.icl with a new task:view_player :: Player -> Task Playerthat uses viewInformation and a ViewOption and the rendering functions defined in exercise 6. to show the current row, ligretto, and hand of the player.

10. 8. Viewing the middle piles • Extend module ligrettoTOP.icl with a new task:view_piles :: [Pile] -> Task [Pile]that uses viewInformation and a ViewOption and the rendering functions to show the currently played piles of cards in the middle of the table.

11. 9. Add people • In the browser, start the task 'Manage users'. • In the opened task, choose the menu 'Import & export' command 'Import demo users'. • This adds the following users to your system: Alice, Bob, Carol, Dave, Eve, and Fred.Their usernames and passwords are: alice, bob, carol, dave, eve, and fred. • Tip: • after adding these users you can log out of the application and log in again as one of the newly registered users.

12. 10. Invite friends • A game of Ligretto is played with 2, 3, or 4 people. • Add the following task function to ligrettoTOP.icl: • invite_friends :: Task [User] • invite_friends • = enterSharedMultipleChoice "Select friends to play with" [] users • >>= \friends ->  • Finish  in such a way that only selections with the correct number of players are accepted • Tip: • after adding these users you can log out of the application and log in again as one of the newly registered users.

13. 11. Shared data source • It is natural to model the 'middle' cards by means of a shared data source because all players have access to the middle cards. • Add the following shared data source to ligrettoTOP.icl: • middle_state :: Shared Middle • middle_state = sharedStore  • Finish  with an appropriate initial value for the middle cards. • It is convenient to model each individual player also by means of a shared data source because this gives you easy access to updates. • Add the following shared data source to ligrettoTOP.icl: • player_state :: Color -> Shared Player • player_state color = sharedStore ("player " <+++ color)  • Finish  with an appropriate initial value for a player with the given color.

14. 12. Viewing the middle piles, now as shared view • Alter the task of assignment 8. (viewing the middle piles) to a viewSharedInformation task that displays the middle_state shared data source. • Alter the task of assignment 7. (viewing a player) to a viewSharedInformation task that displays the player_state of a player of some color.

15. 13. One player plays a game of Ligretto • It is about time to learn a player how to play a game of Ligretto. Create for this purpose a new task function, game. This task function encompasses the following steps: • obtain a random integer necessary to shuffle the initial cards of the player (get randomInttask) • create an initial player (initial_player function from ligretto.dcl) • store the initial player in the corresponding player_state (assignment 11.) • create a shared view on the middle piles and the player (assignment 12.) • step into a new task, play_cards. (assignment 14.)

16. 14. Playing the cards • play_cards keeps an eye on the middle cards and the player state, and uses that information to decide possible future actions. • Add the following task function to ligrettoTOP.icl: • play_cardscolor • = watch (player_statecolor>+<middle_state) • >>* • Study the new functions in this suggested structure: • watch • >+< • >>* • Finish  with appropriate actions (OnAction): • the player can put a row card on a (new) pile in the middle • the player can put a discard hand card on a (new) pile in the middle • the player can take the next three cards of the concealed pile • the player can shuffle all hand cards to restart with the concealed pile • Finish  with an appropriate predicate (OnValue): • immediately when the ligretto pile is empty, return the color of the player

17. 15. All players play a game of Ligretto • You now have all ingredients to finish the main task: play_ligretto. This task encompasses the following steps: • invite friends to a game of Ligretto (assignment 10.) • clearing the middle_state pile to a correct value (assignment 11.) • use anyTaskto let all players play a game of Ligretto (assignment 13.) at the same time. The first player with an empty ligretto pile terminates this anyTask. • congratulate the winner! • Tip: • the anyTaskcombinator evaluates all tasks in its list until the first task that uses the return task function • a player is assigned work by means of the @: combinator

18. 16. Suggestions for improvements… • There are a quite some options to extend this little case study: • create better looking cards, e.g. by means of jpeg files • currently the final score is not computed, this can be added • a player who makes an illegal move can be given a small time penalty • try to make a task that plays Ligretto itself (probably with some random timer to make it fair…) • …