在数组的初始化中使用前一个元素的值

Question

所以我找到了this code works：

class DrawImage(QtWidgets.QWidget):    
    def __init__(self, parent):
        QtWidgets.QWidget.__init__(self, parent)
        self.move(150,50)
        self.setFixedSize(100,100)   
        self.startA = 5
        self.endA = 30

    def paintEvent(self, event):              #use to draw on the canvas
        paint = QtGui.QPainter()
        paint.begin(self)
        paint.setRenderHint(QtGui.QPainter.Antialiasing)
        # make a white drawing background
        paint.setBrush(QtCore.Qt.white)
        paint.drawRect(event.rect())
        paint.setPen(QtCore.Qt.black)
        paint.setBrush(QtCore.Qt.white)   
        paint.drawEllipse(QtCore.QRect(25, 25, 50, 50))    #outer circle

        paint.setPen(QtCore.Qt.yellow)
        paint.setBrush(QtCore.Qt.yellow)   
        paint.drawEllipse(QtCore.QRect(37.5, 37.5, 25, 25))   #middle circle

        paint.setPen(QtCore.Qt.white)
        paint.setBrush(QtCore.Qt.white)   
        paint.drawEllipse(QtCore.QRect(43.75, 43.75, 12.5, 12.5))   #innermost circle

        #where I am trying to implement a half circle
        r = QtCore.QRect(12.5, 12.5, 20, 20)                            #<-- create rectangle
        size = r.size()                                            #<-- get rectangle size
        r.setSize(size*10)                                         #<-- set size
        startAngle = self.startA*16                                #<-- set start angle to draw arc
        endAngle = self.endA*16                                    #<-- set end arc angle
        paint.setPen(QtCore.Qt.black)              #<-- arc color
        paint.setBrush(QtCore.Qt.yellow)   
        paint.drawArc(r, startAngle, endAngle)      

        paint.end()    

这是正式合法的吗？我以为我在这里做一个int foo[] = {0, foo[0] + 1, foo[1] + 2, foo[2] + 4 }; ，但是如果我可以访问先前初始化的元素，则必须进行聚合初始化。

我试图找到关于此行为合法性的官方声明，但我似乎没有。