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)
; m/ N- |  d/ ]4 lIf the case contains Type 4 (or greater) buses with in-service branches then an error condition is
2 P; V  F% M( Treturned. Counts number of islands not containing a Type 3 (swing) bus. It may be inappropriate to
7 z# e/ x+ u8 |% e8 i% fcall 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).
5 s4 c8 q% F: b  w1 P, F; D3 vICODE Error code (integer output):
0 No errors.
-1 No in-service buses remaining.
-2 There are Type 4 buses with in-service branches connected.
>0 Number of islands without a Type 3 bus.
, x; M% E! @# i  z6 l, F3 t" ^太谢谢了