Pointers 派生类型的Fortran 90/95指针

我有一个派生类型，其指针指向第二个派生类型的数组

TYPE vertex
   REAL :: x, y, z
END TYPE

TYPE path
   TYPE(vertex), DIMENSION(:), POINTER :: vertices => NULL()
END TYPE

其目的是使顶点数组的大小可调整，以便可以将任意数量的顶点添加到数组中。我已经创建了代码，将顶点附加到该指针上

SUBROUTINE path_append_vertex(this, x, y, z)
IMPLICIT NONE

!-------------------------------------------------------------------------------
!  Variable declarations.
!-------------------------------------------------------------------------------
TYPE(path), INTENT(inout) :: this
REAL, INTENT(in)   :: x, y, z

!-------------------------------------------------------------------------------
!  Local Variable declarations.
!-------------------------------------------------------------------------------
INTEGER :: status
TYPE(vertex), DIMENSION(:), ALLOCATABLE :: vertices

!-------------------------------------------------------------------------------
!  Start of executable code
!-------------------------------------------------------------------------------
IF (ASSOCIATED(this%vertices)) THEN
! Create a temporary array the same size as current number of vertices. Copy the
! contents of the old array to the new array then delete the old array.
   ALLOCATE(vertices(SIZE(this%vertices)), STAT = status)
   CALL check_status(status)
   vertices = this%vertices
   DEALLOCATE(this%vertices)

! Create a new array with one extra element. Copy the contents of the temporary
! array to the new one the delete the temporary array.
   ALLOCATE(this%vertices(SIZE(vertices) + 1), STAT = status)
   CALL check_status(status)
   this%vertices(1:SIZE(vertices)) = vertices
   DEALLOCATE(vertices)

   this%vertices(SIZE(this%vertices))%x = x
   this%vertices(SIZE(this%vertices))%y = y
   this%vertices(SIZE(this%vertices))%z = z
ELSE
   ALLOCATE(this%vertices(1), STAT = status)
   CALL check_status(status)

   this%vertices(1)%x = x
   this%vertices(1)%y = y
   this%vertices(1)%z = z
ENDIF

END SUBROUTINE

我创建了一些路径对象

TYPE ipch_desc
   ...
   TYPE(path) :: chordPath
END TYPE

SUBROUTINE ipch_desc_construct(this, ...)
...
TYPE (ipch_desc), INTENT(inout)          :: this
...
!  Must NULL out the vertices array or else it will point to the last
!  integration_path created in memory. Not sure why these are defaulting
!  to NULL
this%chordPath%vertices => NULL()

CALL path_append_vertex(this%chordPath, xcart_i(1), xcart_i(2), xcart_i(3))
CALL path_append_vertex(this%chordPath, xcart_f(1), xcart_f(2), xcart_f(3))

!  Check the value of the path vertices.
write(*,*) this%chordPath%vertices

END SUBROUTINE

一切都很好，我得到了每个顶点的正确值。例如，对于我创建的三个路径对象

 -0.33808113528699218        1.0467574437103653       0.10713720000000000      -0.16057879084545851       0.49717960298733294       0.10713720000000000     
 -0.33322243268266594        1.0483142707971911       1.42240000000000010E-003 -0.14945358419461796       0.47017940500485894       1.42240000000000010E-003
 -0.33656460666251325        1.0472460386853264      -0.10629900000000000      -0.15821659220752302       0.49230280357365630      -0.10629900000000000

在代码中使用这些路径对象时

SUBROUTINE ipch_mc_model_compute(a_ipch, ...)
...
TYPE (ipch_desc), INTENT (inout)     :: a_ipch
...
!  Check the value of the path vertices again.
write(*,*) a_ipch%chordPath%vertices
...
END SUBROUTINE

只有前N-1个值保持正确。对于上面创建的相同值

 -0.33808113528699218        1.0467574437103653       0.10713720000000000      -0.16057879084545851       0.49717960298733294       0.10713720000000000     
 -0.33322243268266594        1.0483142707971911       1.42240000000000010E-003 -0.14945358419461796       0.47017940500485894       1.42240000000000010E-003
  0.15094203233057696       6.94277920927416864E-310 -0.10629900000000000       1.63041663127611360E-322  3.01884064661153912E-003  6.94277920927179713E-310

---

无论我创建了多少个

path

对象，第n个总是以错误的值结束。是什么原因造成的？

您的代码似乎正确。你可以简化一下。为什么派生类型路径包含单个变量？可以直接调整VERTEX类型数组的大小，而无需此附加类型。此外，我认为没有理由使用指针；可分配的就足够了。Fortran 2003提供了MOVE_ALLOC，这也提供了简化（如果您正在使用的编译器中有此功能）（请参阅）

---

我知道问题出在哪里了。正在将

ipch_desc

对象构造为一个临时对象，然后将其分配给数组中的一个元素

ipch_desc_arr(icount_chords) = ipch_desc_temp

---

我需要删除这个临时的或重载默认赋值运算符来修复它。

如果您编写自己的答案，您可能也应该接受它。

ipch_desc_arr(icount_chords) = ipch_desc_temp