program vars

*     Program to show some features of variables in fortran
*     Many of the techinques used here are not good programming
*     practice.

      implicit none
      
*     Define some generic type variables
      integer*4 i, j, k
      real*4    r04_1, r04_2
      real*8    r08_1, r08_2   ! Definitions of single variables
      real*8    r08_a(10)      ! 10 element array
      real*8    r08_b(2,3)     ! A 2-row, 3-column matrix
      
      complex*8 c08_1          ! A complex variable (real and imaginary)
      
      logical*4 l04_1, l04_2   ! Logical
      
      character*32 string
      
*****    Tests  ******
*     See what happen when we pass these variables and constants into
*     into subroutine
*     First fill the arrays
      do i = 1, 10
         r08_a(i) = dble(i)
      end do
      do i = 1, 2
         do j = 1, 3
            r08_b(i,j) = dble(i)*1000.d0 + dble(j)
         end do
      end do

*     Now pass these arrays into subroutines and see what happens
*     Correct passage:
      call var_sub_01(j, r08_a, r08_b)
      
      print *,'Return from var_sub_01 ',j

*     In this call, we have changed the dimensioning inside the
*     subroutine.
      
      call var_sub_02(j, r08_a, r08_b)
      print *,'Return from var_sub_02 ',j
      
*     In this call, we have the correct dimensioning but we have
*     changed the variable types
      
      call var_sub_03(j, r08_a, r08_b)
      print *,'Return from var_sub_03 ',j
      
      end
      
CTITLE VAR_SUB_01

      subroutine var_sub_01(n, d1, d2)

*     Test 01: correct declaration of variables
*
      implicit none

* PASSED VARIABLES      
      integer*4 n
      real*8 d1(10), d2(2,3)
      
* LOCAL VARIABLES
      integer*4 i,j
      
****  Write out the values that have been passed.
      write(*,100)
 100  format(/,'VARS: Test 01: Correct declaration of arrays',
     .       ' Type and dimension correct')
      write(*,110) (i,d1(i), i=1,10)
 110  format('Array 1: ',10(i3,F8.2))
      write(*,120) ((i,j,d2(i,j), i=1,2),j=1,3)
 120  format('Array 2: ',10(i3,i3,F8.2))
 
*     Set a return value
      n = 10
     
****  Thats all
      return
      end
           
CTITLE VAR_SUB_02

      subroutine var_sub_02(n, d1, d2)

*     Test 02: Change the declaration but keep the type 
*     the same (you should not do this)
*
      implicit none

* PASSED VARIABLES      
      integer*4 n
      real*8 d1(2,5), d2(6)
      
* LOCAL VARIABLES
      integer*4 i,j
      
****  Write out the values that have been passed.
      write(*,100)
 100  format(/,'VARS: Test 02: In correct declaration of arrays',
     .       ' Type correct, dimension incorrect')
      write(*,110) ((i,j,d1(i,j), i=1,2),j=1,5)
 110  format('Array 1: ',10(i3,i3,F8.2))
      write(*,120) (i,d2(i), i=1,6)
 120  format('Array 2: ',10(i3,F8.2))
 
*     Set a return value
      n = 11
           
****  Thats all
      return
      end
           
CTITLE VAR_SUB_03

      subroutine var_sub_03(n, d1, d2)

*     Test 03: correct dimensions, but wrong type
*
      implicit none

* PASSED VARIABLES      
      integer*4 n
      real*4 d1(10), d2(2,3)
      
* LOCAL VARIABLES
      integer*4 i,j
      
****  Write out the values that have been passed.
      write(*,100)
 100  format(/,'VARS: Test 01: correct dimensioning ',
     .       ' but type is wrong.')
      write(*,110) (i,d1(i), i=1,10)
 110  format('Array 1: ',10(i3,F8.2))
      write(*,120) ((i,j,d2(i,j), i=1,2),j=1,3)
 120  format('Array 2: ',10(i3,i3,F8.2))
 
*     Set a return value
      n = 12
     
****  Thats all
      return
      end