On Monday, February 24, 2014 6:54:59 AM UTC-5, andrew cooke wrote: > > Maybe (I don't think so) Julia needs some kind of concept like abstract > methods, where you can name methods for Number that any subtype must > implement? >
Long ago in Flavors this was called "required methods". With multiple dispatch, you specify a function name and a set of argument types, asserting that for any arguments that are subtypes of the specified types, there will be some applicable method. The advantage of making it an explicit concept in the language, rather than just defining a method that signals an error, is that it can be checked at compile time. It should be a warning since the missing methods could be dynamically loaded later. It is surely useful to find out ahead of run time that you forgot to define a method that some other code is going to call.
