From f16fed3d50fd3d56deb46a3d4641a81460e389de Mon Sep 17 00:00:00 2001 From: David Thompson Date: Wed, 12 Dec 2018 09:20:10 -0500 Subject: Update Chickadee manual and home page for 0.3.0. Better late than never! --- manuals/chickadee/Scripts.html | 209 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 209 insertions(+) create mode 100644 manuals/chickadee/Scripts.html (limited to 'manuals/chickadee/Scripts.html') diff --git a/manuals/chickadee/Scripts.html b/manuals/chickadee/Scripts.html new file mode 100644 index 0000000..c9939f5 --- /dev/null +++ b/manuals/chickadee/Scripts.html @@ -0,0 +1,209 @@ + + + + + + +Scripts (The Chickadee Game Toolkit) + + + + + + + + + + + + + + + + + + + + +
+

+Next: , Previous: , Up: Scripting   [Contents][Index]

+
+
+ +

2.4.2 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: sleep duration
+

Wait duration before resuming the current script. +

+ +
+
Procedure: channel-get channel
+

Wait for a message from channel. +

+ +
+
Syntax: forever body …
+

Evaluate body in an endless loop. +

+ +
+
+

+Next: , Previous: , Up: Scripting   [Contents][Index]

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