Professor Diomar Cesar Lobao

Universidade Federal Fluminense-Volta Redonda, RJ, Brasil

Diomar Cesar


Dept. Ciências Exatas - Exact Science Dept.

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associated.f

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c<pre>
      program association
c
c    Demonstration of association of pointers with targets
c    and testing for the status of association.
c
c<a name="target"><font color="FF0000">
      real, target :: a=1.111, b=2.222
c</font></a>
c<a name="point"><font color="FF0000">
      real, pointer :: p1, p2, p3
c</font></a>
c
c   Associate p1 with a and p2 with b
c
      p1 => a
      write(*,*)' After p1=>a'
c
c   Here is how you can check to see if a pointer is associated
c   With a specific target
c
      if (associated(p1,target=a)) then
         write(*,*) 'p1 is associated with "a"'
      endif
c
c   Check one that we haven't touched
c
c<a name="11"><font color="FF0000">
      if (associated(p2)) then
         write(*,*) 'p2 is associated with a target'
      else
         write(*,*) 'p2 is not associated with a target'
      endif
c</a></font>
c    I can associate a second pointer with the same variable
c
      p2 => a
      write(*,2001)
      write(*,*)' After p2=>a'
c
      write (*,2000) 'p1',p1,'p2',p2,'a',a
c
c   Here is how you can check to see if two pointers are associated
c   with the same target
c
      if (associated(p2,target=p1)) then
         write(*,*) 'p2 and p1 are associated with the same target'
      else
         write(*,*) 'p2 and p1 are not associated with the same target'
      endif
c
c   When I associate one pointer with another, I am making an association
c   with the target of the second pointer
c
      p3 => p2
c
      write(*,2001)
      write(*,*)' After p3=>p2'
      write (*,2000) 'p1',p1,'p2',p2,'p3',p3,'a',a
c
      if (associated(p3,target=a )) then
         write(*,*) 'p3 is associated with "a"'
      else
         write(*,*) 'p3 is not associated with "a"'
      endif
c
c   I can disassociate p2 from it's target, but notice that p3 stays
c   associated with "a".  Notice that although the "associated"
c   function claims p2 is no longer associated with "a", at least on
c   our machine use of p2 still gives the contents of "a" as a result
c   I would consider this to be a bad feature (IBM software only has
c   features, never bugs) in the compiler.
c<a name="6"><font color="FF0000">
      nullify(p2)
c</a></font>
c
      write(*,2001)
      write(*,*) 'After  "nullify(p2)"'
      write (*,2000) 'p1',p1,'p2',p2,'p3',p3,'a',a
c
      if (associated(p2,target=a )) then
         write(*,*) 'p2 is associated with "a"'
      else
         write(*,*) 'p2 is not associated with "a"'
      endif
c
      if (associated(p3,target=a )) then
         write(*,*) 'p3 is associated with "a"'
      else
         write(*,*) 'p3 is not associated with "a"'
      endif
c
c   Even after pointing p2 at a totally different variable
c   p3 stays associated with "a"
c
      p2 => b
c
      write(*,2001)
      write(*,*) 'After   p2 => b     '
      write (*,2000) 'p1',p1,'p2',p2,'p3',p3,'a',a,'b',b
c
      if (associated(p2,target=a )) then
         write(*,*) 'p2 is associated with "a"'
      else
         write(*,*) 'p2 is not associated with "a"'
      endif
c
      if (associated(p3,target=a )) then
         write(*,*) 'p3 is associated with "a"'
      else
         write(*,*) 'p3 is not associated with "a"'
      endif
c
c
 2000 format (a,' =',f6.3, 8(',  ',a,' =',f6.3))
 2001 format(80('-'))
      stop
      end
c</pre>
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