Older type IF structure in Fortran 77

Asked Jul 04 '16 at 08:06

Active Jul 04 '16 at 10:14

Viewed 57 times

I used to coding with Fortran 95, therefore I am not so familiar with Fortran 77. I have a Fortran 77 code which includes the following section:

      REAL*8 Xn, Xend

c     Skip......
      IF (Xn-Xend) 1, 7, 7
7     Xend = Xn

What is the function of IF (Xn-Xend) 1, 7, 7? How can I rewrite it to Fortran 90/95 form?

edited Jul 04 '16 at 10:14

asked Jul 04 '16 at 08:06

Wayne Tsai

I don't think this is valid F77; the indentation of `Xend = Xn` makes one expect an `IF (condition) THEN` line before. – Marcus Müller Jul 04 '16 at 08:10
so maybe you could give us a minimal example of this that would compile? – Marcus Müller Jul 04 '16 at 08:13
5

It is an arithmetic if statement. There are a few other questions on the same topic - have a look at http://stackoverflow.com/q/11124855/1234550 and see if that makes things clear. – IanH Jul 04 '16 at 08:16
@IanH Thanks! I have figured out what it is. – Wayne Tsai Jul 04 '16 at 08:20
Please use tag [tag:fortran]. And others with editing privileges please add the tag there. This way I could not use the instaclose as duplicate. – Vladimir F Героям слава Jul 04 '16 at 10:15

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