/*
** Definition of method type. When retrieving the implementation of a
-** method, this is type of the pointer returned
+** method, this is type of the pointer returned. The idea of the
+** definition of IMP is to represent a 'pointer to a general function
+** taking an id, a SEL, followed by other unspecified arguments'. You
+** must always cast an IMP to a pointer to a function taking the
+** appropriate, specific types for that function, before calling it -
+** to make sure the appropriate arguments are passed to it. The code
+** generated by the compiler to perform method calls automatically
+** does this cast inside method calls.
*/
typedef id (*IMP)(id, SEL, ...);