c++ - boost::assign::map_list_of 枚举类型的值

Question

为什么 boost::assign::map_list_of 会产生 an_enum is not of class type 错误？例如

exp.aggregates = (
                       boost::assign::map_list_of
                       ("a",static_cast<an_enum>(3)),               
                       ("b",static_cast<an_enum>(4)),
                       ("c",static_cast<an_enum>(0))
                 ).operator ltr_and_enum()

Answer 1

你能把它改成这样，看看会发生什么？

map<string, an_enum> myMap = boost::assign::map_list_of
                   ("a",static_cast<an_enum>(3)),               
                   ("b",static_cast<an_enum>(4)),
                   ("c",static_cast<an_enum>(0)));

exp.aggregates = myMap.operator ltr_and_enum();