THIS REPOSITORY SHOWS A SIMPLE WAY TO CODE ENUMERATED TYPES IN FORTRAN

In programming, enumerations (enums, enumerated types) are used to make our source code more readable and also to make the use of objects within our coding more safe. I recently found that many programmers may be unaware about the possibility to code enums in Fortran. (For an example, see this entry in wikipedia: https://en.wikipedia.org/wiki/Enumerated_type#Fortran). The Fortran standard may not specifically mention it, but compilers, and thus the Fortran language, do easily allow to emulate integer-based enumerations since Fortran 95(/90?). The situation has even improved with newer compilers, see the example and explanations below.

See the example code in the src folder.

The example's EnumColors_Values type should be PRIVATE with today's compilers (as shown in the example code), but I believe to remember that Fortran 95 compilers earlier on (back in the 1990s) did require this to be PUBLIC.

To make our (integer-based) enum type more safe to use, we choose somewhat more unique integer values for it, like that:   TYPE (EnumColors_Values), PUBLIC, PARAMETER :: EnumColors = EnumColors_Values (157839,230972,387150)

The src folder does also contain the Fortran_2003_enum_example.f90, using Fortran 2003 enum, bind(c). With that, we found it helpful to use the first enumerator to name the enumeration (Colors):
...
public :: Colors, Blue, Red, Green
enum, bind(c)
  enumerator :: Colors = 0
  enumerator :: Blue = 157839
  enumerator :: Red = 230972
  enumerator :: Green = 387150
end enum
...
integer(kind(Colors)) :: MyColor
MyColor = Green