CODEWITHSUNDEEP
if-statementfortranfortran90fortran77do-loops
Nerdy business
Nerdy business

Reputation: 23

Converting a Go-to statement from FORTRAN 77 to Fortran 90

I am working on a piece of legacy F77 code and trying to convert it to equivalent F90 code. I ran into these lines below and could some one advise if my conversion is correct?

Fortran 77 code:

Subroutine area(x,y,z,d)
do 15 j=1,10
if (a.gt.b) go to 20
15 CONTINUE
20 Statement 1
   Statement 2
   Statement 3
end subroutine

I tried to convert it to F90 and came up as below:

Subroutine area(x,y,z,d)
  dloop: do j=1,10
    if (a>b) then 
      statement 1
      statement 2
      statement 3
    else
      write(*,*) 'Exiting dloop'
      exit dloop
    end if
  end do dloop
end subroutine

Could anyone advise if this methodology is correct? In my results, I am not getting the results that I expect. So there could potentially be a problem with my logic.

Upvotes: 2

Views: 4493

Answers (1)

Alexander Vogt
Alexander Vogt

Reputation: 18098

You got the translation slightly wrong... The first step is to rebuild the do loop, which loops at 15: 

Subroutine area(x,y,z,d)
do j=1,10
  if (a.gt.b) go to 20
enddo
20 Statement 1
   Statement 2
   Statement 3
end subroutine

Now you can see that the goto results in "jumping out of the loop". In this particular example, this equivalent to an exit, and the code can be written as 

Subroutine area(x,y,z,d)
  do j=1,10
    if (a.gt.b) exit
  enddo
  Statement 1
  Statement 2
  Statement 3
end subroutine

Upvotes: 6

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