> On May 22, 2019, at 8:16 PM, Keith Medcalf <kmedc...@dessus.com> wrote: > > Basically, User Defined Types (UDT) were implemented in a fashion analgous to > a C++ class (remember that at this time C++ was just a pre-processor for C > and a C++ class was nothing more than a struct and mangled function names to > operate on the class).
…and a vtable to provide polymorphic dispatch of virtual methods, which is required for OOP. > Basically, when you declared something as a UDT you were giving a "blob" a > type-domain. Whenever you tried to do something with a UDT a "mangled > function name" was generated that took that blob as the first argument Was DB2 using early or late binding of types to blobs? That is, was the type of a blob declared as part of the table column, or were individual blob values tagged with their own types? This makes a huge difference. In the former (early) case the UDTs are just syntactic sugar, while with late-binding they really do act like objects. Late-binding is also required if user-defined functions are to be allowed to return UDTs. > you merely implemented a bunch of functions with the appropriate names that > DB2 would use whenever you referred to that UDT type, rather than using the > builtin functions (this is similar to the way languages like Python implement > classes). Not really; in Python (and Ruby, and Objective-C, and Smalltalk, and sort-of JavaScript…) a class is a dictionary that maps method names to anonymous functions. The functions themselves don't have names. (Sorry to be pedantic, but I'm a bit of a language geek.) —Jens _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
