Function is_true

source/matplot/util/common.cpp:43–46

    }

    bool is_true(std::string_view str) {
        return iequals(str, "on") || iequals(str, "true") ||
               iequals(str, "yes");
    }

    bool is_false(std::string_view str) {
        return iequals(str, "off") || iequals(str, "false") ||