DO循环中IF条件的奇怪标签用法 [英] Strange label usage for an IF condition in a DO loop

问题描述

我不确定哪个版本的Fortran是这段代码，我也不是很擅长，但是这里是我试图理解的一段代码...

  DO 55 J = 1，N 
 IF（KODE（J））55,55,40！ （I，J）=  -  H（I，J）= H（I，J）$ B $ 
 H（I，J）=  -  CH 
 50 CONTINUE 
 55 CONTINUE 
  

在上面给出的循环中，能否帮助我理解第二行的作用，特别是标签55,55,40 p 这是一段代码我试图理解的边界元素书...

解决方案

哇...我还没有看到这个语法一会儿。这是一个Fortran算术IF语句 。 KODE（J）的结果是一个数字。如果它小于零，则使用第一跳，如果它等于零，则使用第二跳，否则使用第三跳。这大致相当于：

  X = KODE（J）
 IF（X.LT.0） 55 
 IF（X.EQ.0）前往55 
前往40 
  

<我的Fortran技能已经明显褪色，但这是我记得的。

I am not sure which version of Fortran is this piece of code, also I am not very good at it but here is the piece of code that I try to understand...

      DO 55 J=1,N  
      IF(KODE(J)) 55,55,40  ! Can not figure out what this line does
   40 DO 50 I=1,N  
      CH=G(I,J) 
      G(I,J)=-H(I,J)
      H(I,J)=-CH
   50 CONTINUE
   55 CONTINUE

In the loop given above, could you help me to understand what the 2nd line does, specifically the labels 55,55,40

This is a code from a boundary element book that I am trying to understand...

解决方案

Wow ... I haven't seen that syntax in a while. That is a Fortran Arithmetic IF Statement. The result of KODE(J) is a number. If it is less than zero, then the first jump is used, if it is equal to zero, then the second jump is used, otherwise, the third jump is used. This is roughly equivalent to:

X=KODE(J)
IF (X.LT.0) GO TO 55
IF (X.EQ.0) GO TO 55
GO TO 40

My Fortran skills have faded significantly, but this is what I remember.

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