一个有意思的问题

li913

但“=”载入是t_father里的eqaul，而不是interface里面的“=”并没有载入。
上面这句话有问题，我试了你的代码，得到恰恰相反的结果。
fortran 不能将子类赋值给父类（ivf2017测试不行，后续版本不清楚），所以 t_father 中的‘=’只用于被继承，实际永远用不到。

[Fortran] 纯文本查看 复制代码

module m_father
  implicit none
  type t_father
     real :: x,y
   contains
     procedure,pass(this),public :: equal
     generic,public :: assignment(=) => equal
  end type t_father
  private equal
contains
  subroutine equal(this,other)
    implicit none
    class(t_father),intent(inout) :: this
    class(t_father),intent(in) :: other
    print*,'t_father'
  end subroutine equal
end module m_father

module m_a
  use m_father
  implicit none

  type,extends(t_father) :: t_a
     real :: z
   contains
     procedure,pass(this),public :: equal
  end type t_a
  private equal
contains
  subroutine equal(this,other)
    implicit none
    class(t_a),intent(inout) :: this
    class(t_father),intent(in) :: other
    print*,'t_a'
  end subroutine equal
end module m_a

module m_b
  use m_father
  implicit none
  type,extends(t_father) :: t_b
     double precision :: z
   contains
     procedure,pass(this),public :: equal
  end type t_b
  private equal
contains
  subroutine equal(this,other)
    implicit none
    class(t_b),intent(inout) :: this
    class(t_father),intent(in) :: other
    print*,'t_b'
  end subroutine equal
end module m_b

module m_interface
  use m_a
  use m_b
  implicit none
  interface assignment(=)
     procedure equal1
     procedure equal2
  end interface
  private equal1,equal2
contains
  subroutine equal1(this,other)
    implicit none
    type(t_a),intent(inout) :: this
    type(t_b),intent(in) :: other
    print*,'equal1'
  end subroutine equal1

  subroutine equal2(this,other)
    implicit none
    type(t_b),intent(inout) :: this
    type(t_a),intent(in) :: other
    print*,'equal2'
  end subroutine equal2
  end module m_interface
  
module m_c
  use m_b
  implicit none
  type,extends(t_b) :: t_c
     integer i
   contains
     procedure,pass(this),public :: equal
  end type t_c
  private equal
contains
  subroutine equal(this,other)
    implicit none
    class(t_c),intent(inout) :: this
    class(t_father),intent(in) :: other
    print*,'t_c'
  end subroutine equal
end module m_c
  
  program test
  use m_a
  use m_b
  use m_father
  use m_c
  use m_interface
  type(t_father) f
  type(t_a) a
  type(t_b) b
  type(t_c) c !c是b的子类
  call f%equal(a)  !调用type中的函数
  call a%equal(b)  !调用type中的函数
  !f=a   !出错，不能将子类赋值给父类
  !b=c  !出错，不能将子类赋值给父类
  a=b !重载，调用equal1
  b=a !重载，调用equal2
  c=b !调用type中的函数
  a=f !调用type中的函数
  pause
  end
  

li913

可能是编译器差异，这就不好搞了。