Page 16 - 《软件学报》2021年第12期

3680 Journal of Software 软件学报 Vol.32, No.12, December 2021

(0, 0) (2, 0) (4, 0) (6, 0) (8, 0) (10, 0) (12, 0)
begin statment Y- N- endif endwhile end
branch branch
Y N N
(2, 2) (8, 2) (10, 2)
if while Y loopbody

Fig.11 Programming flowchart under the layout requirements
图 11 一个满足相应布局要求的程序流程图
(0, 0) (2, 0)
p1 λ := begin stat
(0, 0) (2, 0) (0, 0) (2, 0) (4, 0)
p2 1 stat := 1 statement stat

(0, 0) (2, 0) (0, 0) (2, 0) Y- (4, 0) N- (6, 0) (8, 0)
p3 1 stat := 1 endif stat
branch branch
Y N
(0, 2)
if
(0, 0) (2, 0) (0, 0) (2, 0) (4, 0)
p4 1 stat := 1 endwhile stat
N
(0, 2) (2, 2)
while Y loopbody
(0, 0) (2, 0) (0, 0) (2, 0)
p5 := 1 stat := 1 end

Fig.12 A set of vCGG productions for the programming flowchart
图 12 描述程序流程图的一组 vCGG 产生式

Fig.13 Derivation of the programming flowchart
图 13 上述程序流程图的推导过程