When I am trying to compare members of two different structures, getting the below errors:

error C2676: binary '==': 'main::strRGBSettings' does not define this operator or a conversion to a type acceptable to the predefined operator

error C2678: binary '==': no operator found which takes a left-hand operand of type 'const T1' (or there is no acceptable conversion)

Can someone help how to use the global comparison operator

#include <string>
#include <iostream>

int main()
{
 struct strRGBSettings
    {
        uint8_t red;
        uint8_t green;
        uint8_t blue;
    };

    struct strStandardColors
    {
        static strRGBSettings black() { return { 0x00, 0x00, 0x00 }; }
        static strRGBSettings red() { return { 0xFF, 0x00, 0x00 }; }
        static strRGBSettings blue() { return { 0x00, 0x00, 0xFF }; }
    };

    struct ColorState
    {
        strRGBSettings     RGB;
    };

    ColorState l_colorState;
    if (l_colorState.RGB == strStandardColors::red())
    {
        std::cout << "The color is of type Red " << std::endl;
    }
    return 0;
}

Thank you

CodePudding user response：

As the compiler error says, you need to define operator== for your strRGBSettings struct:

struct strRGBSettings {
    uint8_t red;
    uint8_t green;
    uint8_t blue;
    bool operator==(const strRGBSettings& stg) const {
        return stg.red == red && stg.blue == blue && stg.green == green;
    }
};

If you cannot modify the struct, define operator== as a non-member function:

bool operator==(const strRGBSettings& stg1, const strRGBSettings& stg2) const {
    return (stg1.red == stg2.red && stg1.blue == stg2.blue && stg1.green == stg2.green);
}

Note that this definition cannot go inside main, and you should at least be able to access the struct outside main.