在Fortran中使用派生类型指针和多态目标 [英] Using a derived type pointer and a polymorphic target in Fortran

问题描述

下面列出的Fortran函数使用ifort 11.1编译并执行。但是GFortran 4.6会返回编译器错误：
$ b

THIS_NML =>这是
错误： 1）;尝试将CLASS（UNIT）分配给TYPE（UNIT）。

Fortran代码：

  FUNCTION PROCESS_COMMAND（THIS，CMD，DATA）RESULT（RET）
 CLASS（UNIT），INTENT（INOUT），TARGET :: 
 CHARACTER LEN = *），INTENT（IN）:: CMD 
 CHARACTER（LEN = *），INTENT（IN）:: DATA 
 CHARACTER（LEN = 200）:: STRING 
 INTEGER :: IOS 
 TYPE（UNIT），POINTER :: THIS_NML 
 
！创建一个名称
 NAMELIST / VARS / THIS_NML 
 THIS_NML => THIS 
 RET = 0 
 STRING ='& VARS THIS_NML％'// TRIM（CMD）//'='// TRIM（DATA）//'/'
 
！读取CMD和数据
 READ（STRING，NML = VARS，IOSTAT = IOS）
 RET = IOS 
 
 END FUNCTION PROCESS_COMMAND 
  

因为namelist不能使用多态对象创建，所以派生类型指针 THIS_NML 用于创建名单。任何想法如何使这与GFortran的工作？

解决方案

尝试使用选择类型

  select type（A => THIS）
类型是（UNIT）
在这里，可以将A视为UNIT类型的非多变量变量（如果测试成功）。 
结束选择
  




The Fortran function listed below compiles and executes as expected using ifort 11.1. However GFortran 4.6 returns the compiler error:

THIS_NML => THIS
Error: Different types in pointer assignment at (1); attempted assignment of CLASS(UNIT) to TYPE(UNIT).

Fortran code:

FUNCTION PROCESS_COMMAND(THIS, CMD, DATA) RESULT(RET)
   CLASS(UNIT), INTENT(INOUT), TARGET :: THIS
   CHARACTER(LEN = *), INTENT(IN)     :: CMD
   CHARACTER(LEN = *), INTENT(IN)     :: DATA
   CHARACTER(LEN = 200)               :: STRING
   INTEGER                            :: IOS
   TYPE(UNIT), POINTER                :: THIS_NML

   ! CREATE A NAMELIST
   NAMELIST /VARS/ THIS_NML
   THIS_NML => THIS  
   RET = 0
   STRING = '&VARS THIS_NML%' // TRIM(CMD) // ' = ' // TRIM(DATA) // ' /'

   ! READ CMD AND DATA
   READ(STRING, NML=VARS, IOSTAT=IOS)
   RET = IOS

END FUNCTION PROCESS_COMMAND

Because namelist's cannot be created using polymorphic objects, the derived type pointer THIS_NML is being used to create the namelist. Any ideas how to make this work with GFortran?

解决方案

Try using select type construct. Something like

select type ( A => THIS )
   type is ( UNIT )
      Here you can treat A as nonpolymorphic variable of type UNIT (if the test is succesful).
end select

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