Re: enum sets

On 2024-08-29, Keith Thompson <Keith.S.Thompson+u@gmail.com> wrote:

Thiago Adams <thiago.adams@gmail.com> writes:

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.

>
If I understand you correctly, enum monospaced_font_type is a *subtype*
of enum font_type.
>
Ada has something very similar to this:
>
    type Font_Type is (CASCADIA_FONT, ARIAL_FONT);
    subtype monospaced_font_type is Font_type range CASCADIA_FONT .. CASCADIA_FONT;
>
An Ada subtype is a type with an optionally added *constraint*,
which can be checked at runtime.  But it's hard to see how you'd
add this to C.
>
Given your type definition, how would this behave?
>
    void func(enum monospaced_font_type);
    enum font_type font = ARIAL_FONT;
    func(font);

If enums are to be "safe", the only treatment that makes sense is
a constraint violation (overridable with a cast).

The reverse conversion would not violate a constraint.

Run-time type information in enumeration tags seems like a wrong
stacking of abstractions. Enumerations are something with the help of
which you can implement dynamic typing in a run-time written in C;
you really just want them to be "dumb integers", with some compile-time
checks that catch bugs more often than they don't.

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