Custom Formatters

#include <format>
#include <iostream>
#include <string>
struct Point {
    double x, y;
};
// Custom formatter for Point
template<>
struct std::formatter<Point> {
    // Parse format spec (optional, for custom specifiers)
    constexpr auto parse(format_parse_context& ctx) {
        return ctx.begin();
    }
    
    // Format the Point
    auto format(const Point& p, format_context& ctx) const {
        return std::format_to(ctx.out(), "({}, {})", p.x, p.y);
    }
};
// More complex formatter with format specs
struct Color {
    uint8_t r, g, b;
};
template<>
struct std::formatter<Color> {
    bool use_hex = false;
    
    constexpr auto parse(format_parse_context& ctx) {
        auto it = ctx.begin();
        if (it != ctx.end() && *it == 'x') {
            use_hex = true;
            ++it;
        }
        return it;
    }
    
    auto format(const Color& c, format_context& ctx) const {
        if (use_hex) {
            return std::format_to(ctx.out(), 
                "#{:02X}{:02X}{:02X}", c.r, c.g, c.b);
        }
        return std::format_to(ctx.out(), 
            "rgb({}, {}, {})", c.r, c.g, c.b);
    }
};
int main() {
    Point p{3.5, 7.2};
    std::cout << std::format("Location: {}", p) << std::endl;
    // Output: Location: (3.5, 7.2)
    
    Color red{255, 0, 0};
    std::cout << std::format("Color: {}", red) << std::endl;
    // Output: Color: rgb(255, 0, 0)
    std::cout << std::format("Hex: {:x}", red) << std::endl;
    // Output: Hex: #FF0000
    
    return 0;
}