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？
* k$ U) M, s4 e0 F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
9 q& E$ j6 D! a+ W: icall this subroutine with generators converted; since there will be no Type 3 buses, it will simply
; n4 i3 Z% M$ c; ~4 l( S! _count every island (finding at least one unless there is no working case).
# \  C% f  m' q8 PICODE Error code (integer output):
! K( q: g& ^+ A" o9 e$ r' C/ \0 No errors.
6 c% G% K" c7 w-1 No in-service buses remaining.
$ ^& R  z2 l! W-2 There are Type 4 buses with in-service branches connected.
>0 Number of islands without a Type 3 bus.
太谢谢了