定义于头文件 <sstream>
template< class CharT, class Traits std::char_traits<CharT> > class basic_istringstream;(C11 前)template< class CharT, class Traits std::char_traits<CharT>, class Allocator std::allo…
格式: case expression when condition_01 then result_01 when condition_02 then result_02 ...... when condition_n then result_n else result_default end
表达式expression符合条件condition_01,则返回…