Scripts (The Chickadee Game Toolkit)

From 25c5eac5e6ca1035db1eddd7bea9ac78531da57e Mon Sep 17 00:00:00 2001 From: David Thompson Date: Thu, 28 Dec 2023 11:23:49 -0500 Subject: Delete manuals! Good riddance! These are hosted on files.dthompson.us now! --- manuals/chickadee/Scripts.html | 212 ----------------------------------------- 1 file changed, 212 deletions(-) delete mode 100644 manuals/chickadee/Scripts.html (limited to 'manuals/chickadee/Scripts.html') diff --git a/manuals/chickadee/Scripts.html b/manuals/chickadee/Scripts.html deleted file mode 100644 index b62bb2d..0000000 --- a/manuals/chickadee/Scripts.html +++ /dev/null @@ -1,212 +0,0 @@ - - - - - - -Scripts (The Chickadee Game Toolkit) - - - - - - - - - - - - - - - - - - - - -

5.5.2 Scripts

- -

Now that we can schedule tasks, let’s take things to the next level. -It sure would be great if we could make procedures that described a -series of actions that happened over time, especially if we could do -so without contorting our code into a nest of callback procedures. -This is where scripts come in. With scripts we can write code in a -linear way, in a manner that appears to be synchronous, but with the -ability to suspend periodically in order to let other scripts have a -turn and prevent blocking the game loop. Building on top of the -scheduling that agendas provide, here is a script that models a child -trying to get their mother’s attention: -

(script
-  (while #t
-    (display "mom!")
-    (newline)
-    (sleep 60))) ; where 60 = 1 second of real time
-

- -

This code runs in an endless loop, but the sleep procedure -suspends the script and schedules it to be run later by the agenda. -So, after each iteration of the loop, control is returned back to the -game loop and the program is not stuck spinning in a loop that will -never exit. Pretty neat, eh? -

Scripts can suspend to any capable handler, not just the agenda. -The yield procedure will suspend the current script and pass -its “continuation” to a handler procedure. This handler procedure -could do anything. Perhaps the handler stashes the continuation -somewhere where it will be resumed when the user presses a specific -key on the keyboard, or maybe it will be resumed when the player picks -up an item off of the dungeon floor; the sky is the limit. -

Sometimes it is necessary to abruptly terminate a script after it has -been started. For example, when an enemy is defeated their AI routine -needs to be shut down. When a script is spawned, a handle to that -script is returned that can be used to cancel it when desired. -

(define script (script (while #t (display "hey\n") (sleep 60))))
-;; sometime later
-(cancel-script script)
-

- -

Procedure: spawn-script thunk: Apply thunk as a script and return a handle to it. -

- -

Syntax: script body …: Evaluate body as a script and return a handle to it. -

- -

Procedure: script? obj: Return #t if obj is a script handle. -

- -

Procedure: script-cancelled? obj: Return #t if obj has been cancelled. -

- -

Procedure: script-running? obj: Return #t if obj has not yet terminated or been -cancelled. -

- -

Procedure: script-complete? obj: Return #t if obj has terminated. -

- -

Procedure: cancel-script co: Prevent further execution of the script co. -

- -

Procedure: yield handler: Suspend the current script and pass its continuation to the -procedure handler. -

- -

Procedure: join script: Suspend the current script until script has terminated. -

- -

Procedure: sleep duration: Wait duration before resuming the current script. -

- -

Syntax: wait-until condition

Wait until condition is met before resuming the current script. -

(script
-  (wait-until (key-pressed? 'z))
-  (display "you pressed the Z key!\n"))
-

- -

Syntax: forever body …: Evaluate body in an endless loop. -

- -

- - - - - - -- cgit v1.2.3