请问如何实现在旋转中不断增长的圆弧，当两点重合时，又缩短，这段代码只能实现重合前的部分，不能实现重合后的部分，谢谢大佬指点。

xiaomili

`def setup():
global spanAngle,spanAngleSpeed,spanAngleSpeeda,spanAnglea
size(800,600)
strokeWeight(3)
spanAngle=0
spanAnglea=0
spanAngleSpeed=1
spanAngleSpeeda=0.5
noFill()

def draw():

 global spanAngle,spanAngleSpeed,spanAngleSpeeda,spanAnglea
 t=0
 translate(width/2,height/2)
 background(255)
 spanAngle+=radians(spanAngleSpeed)
 spanAnglea+=radians(spanAngleSpeeda)
 t1=spanAngle%(2*PI)
 t2=spanAnglea%(2*PI)     
 if t2==t1:
     spanAngle+=-radians(spanAngleSpeed)
     spanAnglea+=radians(spanAngleSpeeda)
     arc(0,0,300,300,spanAnglea,spanAngle)
 else:
     arc(0,0,300,300,spanAnglea,spanAngle)          `

xiaomili

def setup():
global spanAngle,spanAngleSpeed,spanAngleSpeeda,spanAnglea
size(800,600)
strokeWeight(3)
spanAngle=0
spanAnglea=0
spanAngleSpeed=1
spanAngleSpeeda=0.1
noFill()

def draw():
global spanAngle,spanAngleSpeed,spanAngleSpeeda,spanAnglea
translate(width/2,height/2)
background(255)
spanAngle+=radians(spanAngleSpeed)
spanAnglea+=radians(spanAngleSpeeda)
spanAngle=spanAngle%(2PI)
spanAnglea=spanAnglea%(2PI)
if spanAnglea>spanAngle:
spanAngleSpeed=-spanAngleSpeed
spanAngleSpeeda=-spanAngleSpeeda
arc(0,0,300,300,spanAnglea,spanAngle)
else:
arc(0,0,300,300,spanAnglea,spanAngle)
这段代码实现了旋转中增长和缩短，但是不能重合

xiaomili

2*PI,代码传上来，少了星号了

paladin

if spanAnglea>=spanAngle:
    spanAngleSpeed=-spanAngleSpeed 
    spanAngleSpeeda=-spanAngleSpeeda
    arc(0,0,300,300,spanAnglea,spanAngle+spanAnglea)
else:
    arc(0,0,300,300,spanAnglea,spanAngle+spanAnglea)

这样就行了