Fortran分配语法 [英] Fortran syntax for assignments
问题描述
Fortran语法让我发疯了!谁能解释我怎么调用该任务(我很确定这也不是正确的术语...).我正在尝试根据值类型分配类型.我有以下内容:
The Fortran syntax is driving me mad! Can anyone explain how I can call the assignment (I'm pretty sure that is not the right terminology either...). I'm trying to assign a type according to the value type. I have the following:
module test_module
implicit none
type :: mytype
integer :: i
real :: r
logical :: l
contains
generic :: assignment(=) => mytype_to_type
procedure, pass(me) :: mytype_to_type
end type mytype
contains
subroutine mytype_to_type(t, me)
implicit none
class(*), intent(inout) :: t
class(mytype), intent(in) :: me
!.. process based on input type
select type (t)
type is (integer)
t = me%i
type is (real)
t = me%r
type is (logical)
t = me%l
class default
stop "none"
return
end select
end subroutine mytype_to_type
end module test_module
program test
use test_module
implicit none
type(mytype) :: t_type
integer :: i = 1
real :: r = 1.
logical :: l = .true.
t_type = i !! how is this supposed to work?
select type(t_type)
type is (integer)
write(*,*) "is int"
type is (real)
write(*,*) "is real"
type is (logical)
write(*,*) "is logical"
class default
return
end select
end program test
这还能行吗?有人可以帮我吗?
Would this even work? Could anyone help me with this?
谢谢!
推荐答案
在支持已定义赋值的子例程中,两个参数使得第一个参数对应于赋值语句的左侧,第二个参数对应于赋值语句的左侧. 1
In a subroutine supporting defined assignment the two arguments are such that the first corresponds to the left-hand side of the assignment statement and the second the right-hand side.1
在这里,您提供的子例程是从my_type
表达式分配给无限多态对象的.这不是您想要的,在左侧看到t_type
.
Here, then the subroutine you provide is assignment from a my_type
expression to an unlimited polymorphic object. This isn't what you want, seeing t_type
on the left.
相反,您应该为my_type
对象提供定义的赋值 .
Instead, you should provide defined assignment to a my_type
object.
subroutine stuff_to_mytype(me,t)
class(mytype), intent(out) :: me
class(*), intent(in) :: t
!.. process based on input type
select type (t)
type is (integer)
me%i = t
type is (real)
me%r = t
type is (logical)
me%l = t
class default
stop "none"
return
end select
end subroutine stuff_to_mytype
也就是说,您可以针对所支持的每种类型使用特定的子例程来执行此操作,而不是使用通用分辨率使用无限制的多态右侧.在这种情况下,您还可以考虑通用结构构造函数(t_type=mytype(i)
).
That said, you could do this with a specific subroutine for each type you support, rather than an unlimited polymorphic right-hand side, with generic resolution. In this case you could also consider generic structure constructors (t_type=mytype(i)
).
1 确切地说,第二个参数是用括号括起来的右侧.
1 Precisely, the second argument is the right-hand side enclosed in parentheses.
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