Question about Goto syntax 2

[jamez05]

I have some code that has a bunch of tags. Some of the tags are just numbers, while others have the word
continue after them. What is the difference between the two?

201	         IF(ISAT.EQ.WLDATM.AND.IAAT.EQ.CARBON) CHKRA=1
	         CHKRI=1
	         GOTO 300

202	         IF(ISAT.EQ.WLDATM.AND.IAAT.EQ.OXEGEN) CHKRA=1
	         CHKRI=1
	         GOTO 300


216	         CONTINUE
	         RN=3
	         GOTO 21900

217	         CONTINUE
	         RN=4
	         GOTO 21900

 

[zeitghost]

Not a lot.

Most people use

200 CONTINUE
IF ( something ) GOTO 999

because it's easier to modify by inserting lines than

200 IF ( something ) GOTO 999

Well, at least it used to be easier to modify if you were using a line editor... if anyone remembers them?

Also commonly used as the terminating statement in DO loops.

 

[xwb]

The tags are labels so you can GOTO them. CONTINUE is just a dummy statement. In your example, you will probably find a GOTO 201, GOTO 202, GOTO 216 and GOTO 217 somewhere in the code. Sometimes the tags are used for loop termination. eg

      DO 999 I = 1, 10, 1
         DO 999 J = 1, 10, 1
         ...
999   CONTINUE

999 will terminate both loops. Sometimes they are used to identify FORMAT statements

      WRITE (10, 888) I, J
888   FORMAT (1X, 'I = ', I2, 'J = ', I9)

They can also be used in assigned goto statements.

      ASSIGN 9876 TO EXIT_CAVE
      ...
      GOTO EXIT_CAVE
      ....
9876  CONTINUE

 

[jamez05]

Thanks for your feedback. Your explanations cleared up my problem. I'm converting the go statements into while loops.

 

[zeitghost]

If you ever see any code with ASSIGNED GOTOs in it, be afraid, be very afraid...

 

[xwb]

It isn't just GOTOs - you can assign them to any label like those for FORMAT statements.

Is there an obfuscated FORTRAN contest???

 

[zeitghost]

I've never tried to GOTO a format statement.

Wonder what it does...

I've only seen the ASSIGNED GOTO used once.

It was a particularly horrid piece of programming that someone used to avoid coding a subroutine... just used ASSIGN 1000 TO JUMP to GOTO the subroutine and ASSIGN 500 TO JUMP to return from it.

Nasty.