求问CHKTRE(ICODE)这个函数

ycjwanok

这边要用到 但看不明白 问问各位  CHKTRE(ICODE)函数是什么作用的？ 返回值个表示什么意思？
手册里给的解释如下
5 ]7 h# w% M/ p1 U$ NCALL CHKTRE(ICODE)
If the case contains Type 4 (or greater) buses with in-service branches then an error condition is
returned. Counts number of islands not containing a Type 3 (swing) bus. It may be inappropriate to
call this subroutine with generators converted; since there will be no Type 3 buses, it will simply
% ?% L% I4 h7 K$ q! x& icount every island (finding at least one unless there is no working case).
# ~' s. L( f5 r5 l! ~ICODE Error code (integer output):
0 No errors.
-1 No in-service buses remaining.
% w0 S# S/ x2 M6 q9 a" c-2 There are Type 4 buses with in-service branches connected.
2 @  f7 J2 I/ g8 b& r1 |# x/ ~. q>0 Number of islands without a Type 3 bus.
) t8 @; C3 D3 r2 G3 I! B太谢谢了