On Mon, Apr 22, 2013 at 12:37:09PM -0600, Owen Densmore wrote: > > In duck typing, one is concerned with just those aspects of an object that > are used, rather than with the type of the object itself. For example, in a > non-duck-typed language, one can create a function that takes an object of > type Duck and calls that object's walk and quack methods. In a duck-typed > language, the equivalent function would take an object of any type and call > that object's walk and quack methods. If the object does not have the > methods that are called then the function signals a run-time error. If the > object does have the methods, then they are executed no matter the type of > the object, evoking the quotation and hence the name of this form of typing. > Duck typing is aided by habitually *not* testing for the type of arguments > in method and function bodies, relying on documentation, clear code and > testing to ensure correct use.
In C++, generic programming, or static polymorphism, is often called duck-typing. If my generic algorithm expexcts the object passed to it have walk, quack and swim methods, then the compiler will not allow you to pass in something that doesn't have those methods, but otherwise there are no other restrictions on the object passed in. This is in contrast to dynamic polymorphism, which is like Java's - the object you pass in must inherit from a base class, which becomes part of the documented interface of the method. "You are only allowed to pass in ducks here, but I don't care what species they are." Side note - Java has "generics", but you can't really do "generic programming", or "duck-typing" in Java, AFAICT. Obviously, in more dynamic languages like Javascript, duck-typing errors must be caught at run time, but in static languages like C++, they are caught at compile time. Cheers -- ---------------------------------------------------------------------------- Prof Russell Standish Phone 0425 253119 (mobile) Principal, High Performance Coders Visiting Professor of Mathematics hpco...@hpcoders.com.au University of New South Wales http://www.hpcoders.com.au ---------------------------------------------------------------------------- ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College to unsubscribe http://redfish.com/mailman/listinfo/friam_redfish.com
