Method validate_mapping

include/CLI/ExtraValidators.hpp:520–543

    /// Check that mapping contains valid units.
    /// Update mapping for CASE_INSENSITIVE mode.
    template <typename Number> static void validate_mapping(std::map<std::string, Number> &mapping, Options opts) {
        for(auto &kv : mapping) {
            if(kv.first.empty()) {
                throw ValidationError("Unit must not be empty.");
            }
            if(!detail::isalpha(kv.first)) {
                throw ValidationError("Unit must contain only letters.");
            }
        }

        // make all units lowercase if CASE_INSENSITIVE
        if(opts & CASE_INSENSITIVE) {
            std::map<std::string, Number> lower_mapping;
            for(auto &kv : mapping) {
                auto s = detail::to_lower(kv.first);
                if(lower_mapping.count(s)) {
                    throw ValidationError(std::string("Several matching lowercase unit representations are found: ") +
                                          s);
                }
                lower_mapping[detail::to_lower(kv.first)] = kv.second;
            }
            mapping = std::move(lower_mapping);
        }
    }

    /// Generate description like this: NUMBER [UNIT]
    template <typename Number> static std::string generate_description(const std::string &name, Options opts) {