What is the <iosfwd> header?
问题 What's the <iosfwd> header used for? Why is it necessary? Any example? 回答1: It's so you can declare, in your own headers, methods that rely on the declarations of iostream types without having to #include the iostream headers themselves, which are large, complex and slow to compile against. Here's a simple example: // foo.h #include <iosfwd> void sucker(std::iostream& is); // foo.cc #include <iostream> void sucker(std::iostream& is) { is >> somevar; } 回答2: As @Marcelo Cantos mentioned, it's