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？
* F2 U  w5 b8 G4 s" p手册里给的解释如下
CALL CHKTRE(ICODE)
5 B& ?' E! V7 r9 o! M+ ~5 Q4 j4 uIf the case contains Type 4 (or greater) buses with in-service branches then an error condition is
1 s4 b8 M( ]4 v( i5 k* Dreturned. Counts number of islands not containing a Type 3 (swing) bus. It may be inappropriate to
  @: w0 R' b5 U) [7 L0 w$ Rcall 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).
& F! L1 M7 |# uICODE Error code (integer output):
' Y3 k! ^) G7 R- [) N$ k! q0 No errors.
' }  R# ^7 ?) @- W* `-1 No in-service buses remaining.
-2 There are Type 4 buses with in-service branches connected.
0 ]1 {4 d8 S9 G9 M/ r4 D8 H>0 Number of islands without a Type 3 bus.
+ _: y- T: u+ q0 @# D& S太谢谢了