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Beginner
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scope of allocatable arrays in modules

I have the following structure:

PROGRAM myPro
USE mMod1
IMPLICIT NONE

REAL t
INTEGER i

CALL proc1

! do something...
! I can access here dt defined in mMod1
! but not myArr1
END PROGRAM myPro
MODULE mMod1
IMPLICIT NONE
REAL dt
REAL, ALLOCATABLE :: myArr1(:,:)


CONTAINS

SUBROUTINE proc1
USE mMod2
CHARACTER(LEN=256) fn
CALL proc2(fn,myArr1)
! I can access here both dt and myArr1
END SUBROUTINE proc1

END MODULE mMod1
MODULE mMod2
IMPLICIT NONE

CONTAINS

SUBROUTINE proc2(fn,myArr1)
CHARACTER(LEN=256), INTENT(IN) :: fn
REAL, ALLOCATABLE :: myArr1(:,:)
INTEGER n
INTEGER, PARAMETER :: dim = 3

! read some input file and determine n

ALLOCATE (myArr1(dim,n))

! fill in the array by reading the rest of the file
END SUBROUTINE proc2

END MODULE mMod2

The question is, the definition of both dt and myArr is the same except that myArr is an allocatable array allocated in a separate module. But I cannot access myArr1 in the main program while I can access dt in the main program. Why? And how to make changes so that I can access it there.

The whole purpose is: I want to read an input file in a separate subroutine into an array (myArr1) and have this array available globaly. This is why I declare it in mMod1. The dimensions of the array are written at the top of the file so I do not know them until I have started reading the file. So the allocation of the myArr1 has to happen inside the separate procedure, I would include it as a separate procedure but it does not work as probably INTERFACE is necessary, so I decided to wrap the procedure in a separate module. 

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2 Replies
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Valued Contributor II
6 Views

It should work the example

It should work the example below runs fine.

module fred
    implicit none
    real, allocatable :: arry(:,:)
    contains
    subroutine bill()
        integer :: istat
        allocate(arry(3,3), stat = istat)
        arry = 0.0
    end subroutine bill
end module fred   

program Console3
    use fred
    implicit none
    integer :: istat
    
    if (allocated( arry ) ) then
        arry=1.0
        arry(1,2) = 2.0
    else
        allocate(arry(3,3), stat = istat)
        arry = 0.0
        arry(3,3) = 3.0
    end if
        
    print *, 'Hello World'
    print *, arry  

end program Console3

 

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Highlighted
Valued Contributor II
6 Views

Hmm  you may have a problem

Hmm  you may have a problem with DIM =3 which is a parameter which is applied at compile time

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