title: How to use this subroutine in fortran
body: <p>I found this subroutine on this link :
  <a href="https://stackoverflow.com/questions/4691824/generate-a-sequence-array-in-fortran?newreg=9c223bfed8a64f3080cfb1a805cde7b1">generate a sequence array in fortran</a></p>
  <p>I want to use this subroutine for my homework.
  But I can't use it and don't know why it didn't play</p>
  <p>Error code is as follows</p>
  <pre><code>Error: Keyword argument requires explicit interface for procedure 'linspace' at (1)
  </code></pre>
  <pre><code>     SUBROUTINE linspace(from, to, array)
  
          REAL(8), intent(in) :: from, to
          REAL(8), intent(out) :: array(:)
          REAL(8) :: range
          integer :: n, i
  
          n = size(array)
          range  = to - from
  
          IF (n == 0) return
          IF (n == 1) then
            array(1) = from
            return
          END IF
  
          DO i=2, n
            array(i) = from + range * (i - 1) / (n - 1)
          END DO
  
        END SUBROUTINE linspace
  </code></pre>
  <pre><code> PROGRAM decay
  
      IMPLICIT NONE
      REAL :: k, c0, dt
      REAL, DIMENSION(15) :: c_e, c_i
      REAL(8) :: t(5)
  
      k = 0.0001
      c0 = 100
      dt = 60*60
      c_e(1) = 100
      c_i(1) = 100
  
      call linspace(from=0.0, to=3600.0, array=t)
  
      print *, t
  
   STOP
   END PROGRAM decay
  </code></pre>