> There's no easy way to tell the C++ compiler, "please make only one version of foo and use callbacks to figure out what it means to += on T". Partial counter

> There's no easy way to tell the C++ compiler, "please make only one version of foo and use callbacks to figure out what it means to += on T". Partial counterpoint: you could use class polymorphism, if T is always a type you control. But you're right in general; C++ doesn't have typeclasses or some other way to create an ad-hoc vtable for, say, int. > Now, if you want monomorphization like C++, call foo() and pass a literal for add_int. But if you don't, then call foo_outline. Does this work through structs of function pointers? Is that the reason it's so powerful? For example, a my_class constructor create_my_class makes the class point to foo_outline, unless it's known to be a hot type, then it points to foo. When you call create_my_class, would the compiler see the values of the pointers, and start inlining foo calls, including if you pass the my_class struct into foo as "this", continuing the inlining?