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hello-world from Chicken Scheme with Box2D
(require-extension coops bind cplusplus-object )
#>
#include <Box2D.h>
// is there a way to access c++ class-fields without these
// two silly helpers?
float getBodyPositionX (b2Body* b) { return b->GetPosition ().x; }
float getBodyPositionY (b2Body* b) { return b->GetPosition ().y; }
<#
; Box2D.scm must be modified: remove constructor and desctuctors of
; private ones (body, fixtures)
(include "Box2D.scm")
(bind "float getBodyPositionX(b2Body* b);")
(bind "float getBodyPositionY(b2Body* b);")
(define (getBodyY obj)
(getBodyPositionY (slot-value obj 'this)))
(define (getBodyX obj)
(getBodyPositionX (slot-value obj 'this)))
(define (pointer obj)
(slot-value obj 'this))
(define (my-new . args) (apply new args))
(define gravity (make-b2Vec2 0 1 ))
(define world (my-new <b2World> gravity))
(print "gravity is " (b2Vec2-x gravity) ", " (b2Vec2-y gravity))
(print "world is " world)
(define groundBodyDef (apply make-b2BodyDef '(2 ; type
0 ;ang
0 ;ang vel
0 ; lin damp
0 ; ang damp
#t ; sleepable
#t ;awake
#f ; fixed rot
#f ; bullet
#t ; active
#f ;userdata
1 ; grav scale
)))
(define boxBody (CreateBody world groundBodyDef))
(define boxShape (my-new <b2PolygonShape> ))
(SetAsBox boxShape 10 10 (make-b2Vec2 0 0) 0)
(CreateFixture boxBody boxShape 0)
(let loop ([ n 30000])
(if (> n 0)
(begin
(Step world (/ 1 60) 6 1)
(print "body pos = " (getBodyPositionY (pointer boxBody)))
(loop (sub1 n)))))
(repl)
(delete world)
;(SetGravity world (make-b2Vec2 0 -1))
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