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-rw-r--r--doc/api/scripting.texi22
-rw-r--r--sly/actor.scm13
2 files changed, 35 insertions, 0 deletions
diff --git a/doc/api/scripting.texi b/doc/api/scripting.texi
index ca2cfd4..299cf0f 100644
--- a/doc/api/scripting.texi
+++ b/doc/api/scripting.texi
@@ -221,6 +221,28 @@ transformed.
@end deffn
+@deffn {Scheme Procedure} action-effect-lift @var{proc}
+Create an action constructor from @var{proc}, a procedure of any
+number of arguments, whose first two arguments are the world being
+transformed and the game object being acted upon. The actions
+returned from this new procedure specify that @var{proc} should be
+performed as an effect on the world, and do not change the actor
+itself.
+
+@example
+;; Theoretical procedure that spawns a new enemy next to the current
+;; enemy actor.
+(define (spawn-enemy world enemy type)
+ (add-enemy world (enemy-position enemy) (make-enemy type))
+
+(define spawn-enemy* (action-effect-lift spawn-enemy))
+
+;; Create a new action that spawns a goblin.
+(spawn-enemy* 'goblin)
+@end example
+
+@end deffn
+
@deffn {Scheme Procedure} both @var{a} @var{b}
Peform action @var{a} immediately followed by action @var{b}. When
the action is run, the remainder of both @var{a} and @var{b} are
diff --git a/sly/actor.scm b/sly/actor.scm
index fd21a64..5b6d7e3 100644
--- a/sly/actor.scm
+++ b/sly/actor.scm
@@ -37,6 +37,7 @@
call-with-actor
action-lift
+ action-effect-lift
idle
both
then
@@ -106,6 +107,18 @@ transformed."
effects
(apply proc object args)))))
+(define (action-effect-lift proc)
+ "Create an action constructor from PROC, a procedure of any number
+of arguments, whose first two arguments are the world being
+transformed and the game object being acted upon. The actions
+returned from this new procedure specify that PROC should be performed
+as an effect on the world, and do not change the actor itself."
+ (lambda args
+ (lambda (world effects object)
+ (values #f
+ (list (lambda (world) (apply proc world object args)))
+ object))))
+
(define (idle world effects object)
"Do nothing. Do not change OBJECT nor add anything to EFFECTS."
(values #f effects object))