Re: enum sets

On 29/08/2024 04:33, David Brown wrote:

On 29/08/2024 01:42, Thiago Adams wrote:

I am wondering how useful would be to have enum sets.
>
Let´s say you have a function that accepts only monospaced fonts.Then you can use enum monospaced_font_type. Or a switch case where you need to check all and only monospaced_font_type.
>
But at same type you can store at same object monospaced_font_type or font_type.
>
enum font_type
{
     enum monospaced_font_type
     {
         CASCADIA_FONT,
     },
     ARIAL_FONT
};
>
This could be arranged in any way.
>

 I think this could have some use-cases, but I suspect that often you would want to have separate enumerations defined first, then combine them with a sum type (aka variant, tagged union, discriminated type, etc.).
  enum monospaced_font_type {
     cascadia
};
 enum proportional_font_type {
     arial
};
 typedef struct {
     enum { is_monospaced_font_type, is_proportional_font_type } tag;
     union {
         enum monospaced_font_type mf;
         enum proportional_font_type pf;
     }
} font_type;
 

One of my motivations was that I have a big enum and sometimes I need to check in switch cases all values of some type.
For instance, let's say
enum E {A, B, C, D /*until Z*/};
And I need to check a subset  for instance  A, B
To have a warning if I miss some item I need to include all cases.
void f(enum E e)
{
    switch(e)
    {
      case A:
      case B:
      break;
      case C:
      //..Z
      break;
    }
}
//warning you missing D case.
The  problem this is not practical when  the number of items is too big.
Using default:break; makes it practical but then the warning disappears.
With this enum set idea the code would be
enum E {
    enum Subset {A, B}
    ,
    C,
    D /*until Z*/
};
void f(enum Subset e)
{
    switch(e)
    {
      case A:
      break;
    } //warning you miss case  B
}