使用假定秩的Fortran数组作为派生类型组件 [英] Using assumed-rank Fortran array as derived type component

问题描述

假设我有一个派生类型（派生类型） 结果与数据组件（除其他外）：

 type，public :: Result 
 private $ b $ class（*），allocatable :: data 
 ... 
结束类型
  

它由某个过程初始化（从接口 Result ）：
$ b $ pre $ 函数init（数据）结果（this）
类型（结果）:: this
类（*），intent（in）:: data

allocate（this％data，source = data）
结束函数
pre>

这对于标量数据来说工作得很好，但我不确定如何设置它以适用于任意级别的数据。我知道过程可以接受假定的参数，所以 init（data）函数中的 data 可以是 data（..），但我不确定是否可以指定派生类型属性 this％data 作为假定rank？

另一种我认为这样做的做法是将任意级别的数据存储为标量，如果Fortran中可能存在这样的情况？这相当于使用 serialize（） 和 unserialize（）函数。如果任何人有类似的方法的指导，我会非常感激。

最终，我想能够做到这样的事情：

$ p $ type（Result）:: scalarResult
type（Result）:: 2DResult

scalarResult = Result（ data = 1.234）
2DResult = Result（data = [[1,2,3]，[4,5,6]]）


解决方案

不可能拥有假定的等级派生类型组件。你需要找到另一个解决方案，比如弗拉基米尔建议的。另一种想法是存储数据和等级的C_LOC，并调用一个C例程来构造一个适当的C描述符，然后用一个假定秩参数调用回Fortran例程。

请记住，您无法在Fortran中使用假定的排名做很多事情 - 直到F2015，SELECT RANK才会存在。

I'm looking for some general advice as to the best approach to creating a derived type that stores arbitrary data with arbitrary rank.

Say I have a derived type Result with a data component (amongst others):

type, public :: Result
    private
    class(*), allocatable :: data
    ...
end type

which is initialised by some procedure (called from an interface Result):

function init(data) result(this)
  type(Result) :: this
  class(*), intent(in) :: data

  allocate(this%data, source=data)
end function

This works fine for scalar data, but I'm unsure about how to go about setting it up for arbitrary-rank data. I know procedures can accept assumed-rank parameters, so data in the init(data) function could be data(..), but I'm not sure it's possible to specify the derived type property this%data as being a assumed rank?

The other way I thought of doing it would be to store the arbitrary rank data as a scalar, if such a thing is possible in Fortran? This would be equivalent to using the serialize() and unserialize() functions in PHP. If anyone has any guidance on a similar approach, I'd be very grateful.

Ultimately I'd like to be able to do something like this:

type(Result) :: scalarResult
type(Result) :: 2DResult

scalarResult = Result(data=1.234)
2DResult = Result(data=[[1,2,3],[4,5,6]])

解决方案

It's not possible to have an assumed rank derived type component. You'll need to find another solution, such as what Vladimir suggests. Another idea, which is sort of a kluge, is to store the C_LOC of the data and the rank, call out to a C routine that constructs an appropriate C descriptor and then calls back in to a Fortran routine with an assumed-rank argument.

Do keep in mind that you can't do a lot with assumed rank in Fortran - SELECT RANK doesn't exist until F2015.

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