Starting a how it works explanation

Author: williamhaarhoff

docs/how_it_works.md

@@ -0,0 +1,39 @@
+```cpp
+ARCHETYPE_DEFINE(basic_interface, (
+  ARCHETYPE_METHOD(int, func0, const char *)
+))
+```
+
+This expands to a structure that contains four substructures. These are:
+
+-  **A protected component structure.** This implements the vtable as a stackable layer, but does not have a public interface. 
+-  **A public view class.** Stacks the component on top of a base, and provides the public bind() function while keeping the internal component layer private. 
+-  **A public ptr class.** This gives an alternative public interface that allows using pointer syntax.
+-  **A public templated check<T> structure.** This is used for testing and verifying that type T meets the interface specification using SFINAE
+
+## Component structure:
+Almost all of the core functionality exists within the protected component that exists within the `basic_interface` struct. I'll start with a stripped down version, and explain how the functionality is build up. 
+
+The component itself is templated on a base class. It will inherit from a particular base, and stack its functionality on top without using any virtuals. All the component cares about is being able to access the `B::_obj` that is a `void *` protected member variable defined by the base class. This `B::_obj` is going to store a `void *` of the object that will get bound. 
+
+```cpp
+template <typename B = archetype::Base> 
+class component : public B {
+  protected:
+  using B::_obj;
+};
+```
+
+For the component to actully be useful, it needs to implement the interface that we've defined. It does this by implementing a `vtable` through function pointers and functions. In this case we have a protected function pointer: `int (*_func0_stub)(void *obj, const char *);` 
+
+```cpp
+template <typename B = archetype::Base> 
+class component : public B {
+  public:
+  int func0(const char *arg0) { return _func0_stub(_obj, arg0); }
+
+  protected:
+  int (*_func0_stub)(void *obj, const char *);
+  using B::_obj;
+};
+```