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
CALL 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
2 B# B" ^; R$ x4 D/ g' {; D& m# icall this subroutine with generators converted; since there will be no Type 3 buses, it will simply
count every island (finding at least one unless there is no working case).
# d$ c' N! R# J7 UICODE Error code (integer output):
0 No errors.
5 P' x, o0 O1 Q4 [( ~-1 No in-service buses remaining.
; k' t6 i$ a3 C- m( N2 o-2 There are Type 4 buses with in-service branches connected.
>0 Number of islands without a Type 3 bus.
太谢谢了