a dirty enough string.format() function for pre-c++20 for copy pasta

sformat.hpp

// string format
// by cos 2020. licensed under MIT
#pragma once

#include <string>
#include <sstream>

namespace detail {
    template<class CharT>
    void format_impl(std::basic_ostringstream<CharT> &oss, const CharT *s) {
        oss << s;
    }

    template<class CharT, class V, class ...Args>
    void format_impl(std::basic_ostringstream<CharT> &oss, const CharT *s, const V &v, const Args& ...args) {
        while (*s) {
            // if have input like "{{haha", where there is a left brace not followed by a right brace,
            // ignore this
            if (*s == '{' && *(s+1) == '}') {
                oss << v;
                return format_impl(oss, (s+2), args...);
            }
            oss << *s++;
        }
        throw std::runtime_error("extra arguments provided to format");
    }
}

/**
 * simple string.format. usage: format("hello {}th {}!", 5, "Alice")
 * produces "hello 5th Alice!"
 */
template<class CharT, class ...Args>
std::basic_string<CharT> format(const CharT *s, const Args& ...args) {
    std::basic_ostringstream<CharT> oss;
    detail::format_impl(oss, s, args...);
    return oss.str();
}