fix up chipmunk.demo, add a MAIN:

extra/chipmunk/demo/demo.factor

@@ -1,7 +1,7 @@
 ! Copyright (C) 2010 Erik Charlebois
 ! See http:// factorcode.org/license.txt for BSD license.
-USING: accessors chipmunk.ffi classes.struct game.worlds kernel locals
-math method-chains opengl.gl random sequences specialized-arrays
+USING: accessors alien chipmunk.ffi classes.struct game.worlds kernel
+locals math method-chains opengl.gl random sequences specialized-arrays
 specialized-arrays.instances.alien.c-types.void* ui ui.gadgets.worlds
 ui.pixel-formats ;
 IN: chipmunk.demo
@@ -53,7 +53,10 @@ CONSTANT: image-bitmap B{
     cpBodyAlloc 1.0 NAN: 0 cpBodyInit
     x y cpv >>p :> body
     cpCircleShapeAlloc body 0.95 0 0 cpv cpCircleShapeInit
-    [ shape>> 0 >>e ] [ shape>> 0 >>u ] bi drop ;
+    dup shape>>
+        0 >>e
+        0 >>u
+        drop ;
 
 TUPLE: chipmunk-world < game-world
     space ;
@@ -88,7 +91,7 @@ M:: chipmunk-world draw-world* ( world -- )
     space arbiters>>
     [ num>> ] [ arr>> swap <direct-void*-array> ] bi [
         cpArbiter memory>struct
-        [ numContacts>> ] [ contacts>> swap <direct-cpContact-array> ] bi [
+        [ numContacts>> ] [ contacts>> >c-ptr swap <direct-cpContact-array> ] bi [
             p>> [ x>> ] [ y>> ] bi glVertex2f
         ] each
     ] each
@@ -109,7 +112,7 @@ M:: chipmunk-world begin-game-world ( world -- )
                 x image-width 2 / - 0.05 0.0 1.0 uniform-random-float * + 2 *
                 image-height 2 / y - 0.05 0.0 1.0 uniform-random-float * + 2 *
                 make-ball :> shape
-                space shape body>> cpSpaceAddBody drop
+                space shape shape>> body>> cpSpaceAddBody drop
                 space shape cpSpaceAddShape drop
             ] when
         ] each
@@ -119,10 +122,12 @@ M:: chipmunk-world begin-game-world ( world -- )
     body -1000 -10 cpv >>p drop
     body 400 0 cpv >>v drop
 
-    space cpCircleShapeAlloc body 8 0 0 cpv cpCircleShapeInit cpSpaceAddShape :> shape
-    shape
-    [ shape>> 0 >>e drop ]
-    [ shape>> 0 >>u drop ] bi ;
+    space cpCircleShapeAlloc [ body 8 0 0 cpv cpCircleShapeInit cpSpaceAddShape drop ] keep
+        :> shape
+    shape shape>>
+        0 >>e
+        0 >>u
+        drop ;
 
 M: chipmunk-world end-game-world
     space>>
@@ -145,3 +150,4 @@ M: chipmunk-world end-game-world
         open-window
     ] with-ui ;
 
+MAIN: chipmunk-demo