Defining a function returning an array

Question

I have the following code:

    Program function_as_an_array
    implicit none
    integer:: i
    integer, parameter:: N=10
    real*8:: x(N),y(N),f(N)

            


        

Answer 1

This is working for me:

Program function_as_an_array
implicit none
integer:: i
integer, parameter:: N=10
real*8 :: x(N),y(N),f(N)
interface func
  function func(x,N) result(f)
    implicit none
    integer N
    real*8:: x(N),f(N) 
  end function
end interface

do i=1,N
  x(i)=float(i)
end do

f = func(x,N)

open(unit=20, file='test.dat')
do i=1,N
  y(i)=f(i)
  write(20,*) x(i),y(i) 
end do
close(20)
Stop 
End Program function_as_an_array


function func(x,N) result(f)
implicit none
integer i, N
real*8:: x(N),f(N) 

do i=1,N
   f(i)=x(i)**2
end do

end function

You need to:

• use result for an array-valued return variable [edit] or specify func as real*8:: func(N). See the comments for details.
• use an explicit interface for external functions (or a module which has an implicit interface, see Jonathan Dursi's answer )

Then, you can directly assign the return value of the function to the array.