Self study guide: Fortran 95 - University of Cambridge

program set
implicit none
real :: a, b
! Read in value of a
read(*,*) a
call setval(b)
write(*,*) b
contains
subroutine setval(x)
real :: x
x = a ! value of a is from main program
end subroutine setval
end program set
This program is very contrived, it simply sets the value of the argument of the call to
setval to the value of the variable a in the main program. In this example a is a
variable global to the main program and the subroutine setval.
5.5 Passing arrays to subroutines and functions
Arrays can of course be used as arguments to subroutines and functions,
however there are one or two special considerations.
5.5.1 Size and shape of array known
If the size and shape of the array are known, one can simply repeat the definition in
the subroutine when the arguments are declared. For example, if v and r are vectors
of length 3 a subroutine declaration in which they are passed would look like:
subroutine arr1(v, r)
real :: v(3)
real :: r(3)
and of course you could have used the alternative form using dimension instead:
subroutine arr1(v, r)
real, dimension(3) :: v, r
5.5.2 Arrays of unknown shape and size
The problem is how to deal with arrays of unknown length. This is important when
for example we wish to write a subroutine which will work with arrays of many
different lengths. For example, we may wish to calculate various statistics of an
array. We can in this case use the following definition:
35