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fortran
Peaceful
Peaceful

Reputation: 5470

Updating a Fortran variable by addition

In my Fortran code I need to update many variables by adding something to them. For example, if x is my variable, I may need to do something like this:

x = x + 1

The problem is that my variables are array elements and have big names etc so repeating x in the above equation is cumbersome task. In Python for example we have the += operator to achieve this. Do we have something similar in Fortran?

Upvotes: 7

Views: 6408

Answers (2)

PetrH
PetrH

Reputation: 730

"The problem is that my variables are array elements and have big names etc so repeating x in the above equation is cumbersome task."

Well, if this is your only problem then the simplest and cleanest solution is to use the associate construct (I use it all the time for exactly this purpose):

ASSOCIATE( x => variable_with_really_long_name, &
           y => another_one)

    ! some calculations here

    x = x + 1

    ! some calculations here again

end associate

Upvotes: 6

Alexander Vogt
Alexander Vogt

Reputation: 18118

No, Fortran does not have this operator. However, you could implement a subroutine to do so:

elemental subroutine my_incr( var, incr )
  implicit none
  integer,intent(inout) :: var
  integer,intent(in)    :: incr

  var = var + incr
end subroutine

Then you could call that in your code:

! ...
call my_incr( x, 1 )
! ...

Due to the elemental nature of the subroutine, you can also perform this operation on arrays:

! ...
call my_incr( array(:), 1 )
! ...

Upvotes: 12

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