What type do I use in the constructor to initialize a member variable defined by a nameless enum?-CodePudding

I have a struct containing a member variable category which I guess is of type "nameless enum".

struct Token {
    Token();
    enum {
            NUMBER, VARIABLE, PLUS, MINUS, PRODUCT, DIVISION, POWER, SIN, COS
    } category;
    union { 
        char variable;
        double number;
    };
};

As you can see I also have a constructor Token(). I would like to be able to use the constructor like this:

Token my_token(Token::NUMBER, 5);

Instead of doing something like this:

Token my_token;
my_token.category = Token::NUMBER;
my_token.number = 5;

My question now is, what types do I use for the constructor? I tried something like this:

//declaration
Token(int category, int number);

//definition
Token(int category, int number) : category(category), number(number) {}

But then when I try to initialize an object of the Token struct I get:
error: invalid conversion from ‘int’ to ‘Token::<unnamed enum>’ [-fpermissive]

I would like to keep the enum inside of the struct, some help with what type to use to initialize the union would also be appreciated.

CodePudding user response：

Something like this?

struct Token {
    enum EN {
            NUMBER, VARIABLE, PLUS, MINUS, PRODUCT, DIVISION, POWER, SIN, COS
    } category;
    union { 
        char variable;
        double number;
    };
    Token(const EN c, const double n) noexcept : category(c), number(n) {}
    //... Other constructors...
};

int main()
{
    Token t(Token::NUMBER, 3.4);
}

But I'd assign the category internally