如何覆盖fortran中的结构构造函数 [英] How to override a structure constructor in fortran

问题描述

目前是否可以覆盖Fortran中的结构构造函数？我已经看到像这样的建议示例（如在Fortran 2003规范）：

Is it currently possible to override the structure constructor in Fortran? I have seen proposed examples like this (such as in the Fortran 2003 spec):

module mymod

  type mytype
    integer :: x
    ! Other stuff
  end type

  interface mytype
    module procedure init_mytype
  end interface

contains
  type(mytype) function init_mytype(i)
    integer, intent(in) :: i
    if(i > 0) then
      init_mytype%x = 1
    else
      init_mytype%x = 2
    end if
  end function
end

program test
  use mymod
  type(mytype) :: x
  x = mytype(0)
end program

这基本上会由于冗余变量名称（例如错误：'mytype'的DERIVED属性与（1）处的PROCEDURE属性冲突）。 fortran 2003示例的逐字副本产生类似的错误。我试过这个在gfortran 4.4，ifort 10.1和11.1和他们都产生相同的错误。

This basically generates a heap of errors due to redundant variable names (e.g. Error: DERIVED attribute of 'mytype' conflicts with PROCEDURE attribute at (1)). A verbatim copy of the fortran 2003 example generates similar errors. I've tried this in gfortran 4.4, ifort 10.1 and 11.1 and they all produce the same errors.

我的问题：这只是fortran 2003的一个未实现的功能？

My question: is this just an unimplemented feature of fortran 2003? Or am I implementing this incorrectly?

编辑：我遇到了一个错误报告和公布的补丁到gfortran关于这个问题。但是，我试过使用11月的gcc46版本，没有运气和类似的错误。

I've come across a bug report and an announced patch to gfortran regarding this issue. However, I've tried using a November build of gcc46 with no luck and similar errors.

编辑2：上面的代码似乎使用Intel Fortran 12.1.0。

Edit 2: The above code appears to work using Intel Fortran 12.1.0.

推荐答案

我查阅了我的Fortran 2008标准的副本。这允许您定义与派生类型具有相同名称的通用接口。我的编译器（Intel Fortran 11.1）不会编译代码，所以我离开怀疑（没有2003标准的副本），这是Fortran 2003标准的一个尚未实现的功能。

I consulted my copy of the Fortran 2008 standard. That does allow you to define a generic interface with the same name as a derived type. My compiler (Intel Fortran 11.1) won't compile the code though so I'm left suspecting (without a copy of the 2003 standard to hand) that this is an as-yet-unimplemented feature of the Fortran 2003 standard.

此外，您的程序中有错误。您的函数声明：

Besides that, there is an error in your program. Your function declaration:

  type(mytype) function init_mytype
    integer, intent(in) :: i

指定函数说明中不存在的参数的存在和意图，应该将其重写为：

specifies the existence and intent of an argument which is not present in the function specification, which should perhaps be rewritten as:

  type(mytype) function init_mytype(i)

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