Fortran 2003 中的内在赋值和多态性 [英] Intrinsic Assignment and Polymorphism in Fortran 2003

问题描述

我尝试向这个模块，由 @VladimirF 编写，在 Fortran 2003 中实现了一个通用链表.我希望能够输出为方便起见，将列表的内容作为一个数组，所以我在一个名为 lists.f90 的文件中的列表模块中添加了以下过程:

I tried adding a procedure to this module, written by @VladimirF, that implements a generic linked list in Fortran 2003. I wanted to be able to output the contents of the list as an array for convenience, so I added the following procedure to a lists module in a file called lists.f90:

  subroutine list_as_array(self, arrayOut)
    class(list),intent(inout) :: self
    class(*),dimension(1:self%length),intent(out) :: arrayOut
    integer :: i
    type(list_node), pointer :: nodeIter
    nodeIter = self%first
    do i = 1,self%length
      arrayOut(i) = nodeIter%item  ! <---ERROR here
      if (i<self%length) then
        nodeIter = nodeIter%next
      end if
    end do
  end subroutine list_as_array

ifort 18.0.0 给出以下错误:

lists.f90(324): error #8304: In an intrinsic assignment statement, variable shall not be a non-allocatable polymorphic.   [ARRAYOUT]
      arrayOut(i) = nodeIter%item
------^

我是 F2​​003+ 中的多态性新手，所以我不理解错误消息或其上下文.出了什么问题，如何解决?

I'm new to polymorphism in F2003+, so I do not understand the error message or its context. What's wrong, and how can it be fixed?

推荐答案

错误信息就是它所说的意思.描述内在赋值语句的 Fortran 2008 标准说:如果变量是多态的，它应该是可分配的，而不是 coarray"arrayOut 是 CLASS(*)，它是多态的.只能分配可分配的多态.

The error message means what it says. The Fortran 2008 standard, describing the intrinsic assignment statement, says: "if the variable is polymorphic it shall be allocatable and not a coarray" arrayOut is CLASS(*), which makes in polymorphic. Only allocatable polymorphics can be assigned to.

至于如何解决"，这需要更多的上下文.

As to "how to fix it", that would need some more context.

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