错误：具有非零等级的part-ref右侧的部分名称具有ALLOCATABLE属性 [英] Error: The part-name to the right of a part-ref with nonzero rank has the ALLOCATABLE attribute

问题描述

我想使用子程序sum_real访问数组中派生类型的数组元素。那就是：总结所有人的体重第一项。

  type my_type 
 real，dimension（:)，allocatable :: weight 
 real :: total_weight 
结束类型my_type 
 
 type（my_type），dimension（:)，allocatable :: people 
 type（my_type）:: answer 
 
 allocate（people （2））
分配（人（1）％权重（2））
分配（人（2）％权重（2））
 
人（1）％权重（1）= 1 
 people（2）％weight（1）= 1 
 people（1）％weight（2）= 3 
 people（2）％weight（2）= 3 
 
 call sum_real（people（:)％weight（1），answer％total_weight）
  

我想要做的与派生类型数组中的答案类似：select entry ，除了我有一个数组派生类型而不是单个元素的分配数组。

但是，我得到一个编译器错误：

 错误＃7828：part-具有非零等级的ref具有ALLOCATABLE属性（6.1.2）。 [WEIGHT] 
  

解决方案

组件是可分配的。引用（ 6.1.2 ）实际上是对官方标准文档的引用，它禁止这一点。

原因很简单，可分配的组件（标量或数组）存储在与派生类型本身不同的内存部分中。因此，如果你写了

 总和（人物％total_weight）
  

或

 人物％total_weight = 0 
  

这是没有问题的， total_weight 不是可分配的，它存储在派生类型，编译器只是进入一个简单的循环，并将一个接一个的字段设置为零。您可以事先知道每个％totalweight 的地址。

另一方面

 总和（人物％权重）
  

或

  people％weight = 0 
  

每个％权重存储在其他地方，并且您没有任何简单公式来计算每个 ％weight（i）。

解决方法是，如果可能的话，修复数组的大小。 b

  real，dimension（2）:: weight 
  

或者使用do循环

$ $ $ $ $ $ $ $ $ $ $ $
S = S + sum（人（i）％重量）
结束做

I would like to access the the elements of an array in a an arrayed derived type using the subroutine sum_real. That is: sum over first entry in the weight for all people.

type my_type
   real, dimension(:), allocatable :: weight
   real :: total_weight
end type my_type

type (my_type), dimension (:), allocatable :: people
type (my_type) :: answer

allocate (people (2))
allocate (people (1)%weight(2))
allocate (people (2)%weight(2))

people (1) % weight(1) = 1
people (2) % weight(1) = 1
people (1) % weight(2) = 3
people (2) % weight(2) = 3

call sum_real ( people (:) % weight(1), answer % total_weight )

What I want to do is similar to the answer found in Array of derived type: select entry, except for the fact that I have an allocated array in an arrayed derived type instead of an single element.

But, I get a compiler error:

error #7828: The part-name to the right of a part-ref with nonzero rank has the ALLOCATABLE attribute (6.1.2).   [WEIGHT]

解决方案

What you try is not possible if your component is allocatable. The reference (6.1.2) is actually a reference to the official standard documents, which prohibits this.

The reason is simple, the allocatable components (scalar or arrays) are stored in a different part of memory than the derived type itself. Therefore if you write

sum(people%total_weight)

or

people%total_weight = 0

it is no problem, total_weight is not allocatable, it is stored within the derived type and the compiler just goes in a simple loop and sets one field after another to zero. You can know the address of each %totalweight beforehand.

On the other hand

sum(people%weight)

or

people%weight = 0

each %weight is stored elsewhere and you don't have any simple formula to compute where is each %weight(i).

The solution is either, to fix the size of the array, if possible

real, dimension(2) :: weight

or use a do loop

s = 0
do i = 1, size(people)
  S = S + sum(people(i)%weight)
end do

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