如何在Fortran中进行几项枚举类型？
我试图在Fortran中声明几种枚举类型。
这个有趣的简单示例很好地说明了我的问题：
program Main
enum, bind(c)
enumerator :: Colors = 0
enumerator :: Blue = 1
enumerator :: Red = 2
enumerator :: Green = 3
end enum
enum, bind(c)
enumerator :: Size = 0
enumerator :: Small = 1
enumerator :: Medium = 2
enumerator :: Large = 3
end enum
integer(kind(Colors)) :: myColor
myColor = Green
if (myColor == Large) then
write(*,*) 'MyColor is Large'
end if
end program Main
我还试图将这种枚举包裹在一种类型中，而其他许多东西都可以，但没有任何事情。
在这里，我可以将颜色与size进行比较。例如，在C中，当我声明color和a size typedef枚举时，我没有这样的问题，因为两种类型是不同的。
在Fortran中具有几种枚举类型是否存在简单的解决方案？
否则，我想像一个具有数字成员的几种类型，该整数成员持有值，然后创建接口以超载我需要的运算符（比较，情感等）。我不确定解决方案是否可能，而且我可以做到。
I tried to declare several enumeration types in Fortran.
This funny simple example illustrates well my problem :
program Main
enum, bind(c)
enumerator :: Colors = 0
enumerator :: Blue = 1
enumerator :: Red = 2
enumerator :: Green = 3
end enum
enum, bind(c)
enumerator :: Size = 0
enumerator :: Small = 1
enumerator :: Medium = 2
enumerator :: Large = 3
end enum
integer(kind(Colors)) :: myColor
myColor = Green
if (myColor == Large) then
write(*,*) 'MyColor is Large'
end if
end program Main
I also tried to enclose this enumeration in a type and many others things but none works.
Here I can compare Colors with Size. In C, for example, when I declare color and a size typedef enum, I have no such problem, because the two types are different.
Does it exist a simple solution to have several enumerated type in Fortran?
Otherwise, I imagine to declare several types with one integer member that holds the value and, after, to create interface to overload the operators I need (comparison, affectation and so on). I am not sure that solution is possible and also, I can do it.
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评论（1）
Fortran在您希望使用的意义上没有枚举类型。 1
Fortran中的枚举是一组枚举者。问题的程序有两个。
枚举者本身是与C相应的枚举类型互操作的（整数）常数。它们是出于C互操作性的目的而存在，并且不提供Fortran内部的类似功能。
枚举者
green和问题中的大型是两个带有值3的整数常数（在某些，可能是不同的类型中）。green ==大型无论常数的类似参数是真实的表达式。Fortran中没有将变量限制为枚举值的机制。常数可以等效地将其声明为
适当的类值（在这种情况下很可能是相同的：
c_int），而Fortran程序将没有区别。如果您想在C和类似语言中存在枚举类型的意义，则必须使用非intrinsic方法（如问题所示）。
1 当前2018年的修订是这种情况。目前，有一个建议下一个修订版（临时2023年），将枚举类型包括在这里所需的内容。该规范在一个特定。
Fortran does not have enumerated types in the sense that you wish to use.1
An enumeration in Fortran is a set of enumerators. The program of the question has two of them.
Enumerators themselves are named (integer) constants of a kind interoperable with C's corresponding enumeration type. They exist for the purposes of C interoperability and not to provide a similar functionality within Fortran.
The enumerators
GreenandLargein the question are two named integer constants with value 3 (of some, possibly different kind).Green==Largeis a true expression whatever the kind parameters of the constants.There is no mechanism in Fortran to restrict a variable to values of an enumeration. The constants could equivalently be declared as
for the appropriate kind values (which are quite likely in this case to be the same:
C_INT) and the Fortran program would know no difference.If you wish to use enumerated types in the sense that they exist in C and similar languages, you will have to use a non-intrinsic approach (as intimated in the question).
1 This is the case for the current, 2018, revision of the language. At this time, there is a proposal for the next revision (provisionally 2023) to include enumerated types closer to what is desired here. This specification is given in 7.6.2 of one particular working draft.