Polymorphism sucks [Was: Paradigms which way to go?]
in [OOP]
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From: Phlip on 7 Jun 2005 11:25 Gerry Quinn wrote: > If you are writing a monolithic piece of software to perform some task, > and things like GUI controls are not involved, you may very well know > what type (as distinct from a generalised 'value') every object is > anyway. If so, polymorphism will not bring anything useful to the > table. Likely enough most of what the OP has been working on is of > this type. Polymorphism will help fold redundancies together - if any. Unless you want to take on _all_ the /Design Patterns/ books... > To say "OO is about polymorphism", in short, is nonsense. Definitions, in engineering, should be short, useful, and distinct. Long rambling definitions don't help discussions. -- Phlip http://www.c2.com/cgi/wiki?ZeekLand
From: topmind on 8 Jun 2005 01:29 > Polymorphism will help fold redundancies together - if any. There are multiple ways to do such. Polymorphism usually (not always) seems to assume that things nicely fit into a mutually-exclusive list of categories or a hierarchy of variations. However, in the real world things are often not so clean. There is no Tree Cop to keep things nice. Polymorphism has a *big rework-cost* to go from IS-A to HAS-A when hierarchies or mutual exclusion fail to provide a sufficient modeling statement. In other words, poly it does not bend with the shape of real-world changes as I observe them. -T- oop.ismad.com
From: Gerry Quinn on 8 Jun 2005 06:50 In article <u%ipe.2164$jS1.720(a)newssvr17.news.prodigy.com>, phlip_cpp(a)yahoo.com says... > Gerry Quinn wrote: > > > If you are writing a monolithic piece of software to perform some task, > > and things like GUI controls are not involved, you may very well know > > what type (as distinct from a generalised 'value') every object is > > anyway. If so, polymorphism will not bring anything useful to the > > table. Likely enough most of what the OP has been working on is of > > this type. > > Polymorphism will help fold redundancies together - if any. It can help that. Sometimes. As 'topmind' observes, it can also trap you somewhere you don't want to be. > Unless you want to take on _all_ the /Design Patterns/ books... > > > To say "OO is about polymorphism", in short, is nonsense. > > Definitions, in engineering, should be short, useful, and distinct. Long > rambling definitions don't help discussions. In the first sentence, you left out "correct". - Gerry Quinn
From: Robert C. Martin on 8 Jun 2005 09:00 On Tue, 07 Jun 2005 15:25:14 GMT, "Phlip" <phlip_cpp(a)yahoo.com> wrote: >Gerry Quinn wrote: >> To say "OO is about polymorphism", in short, is nonsense. This was cross posted to comp.object, so I'm not sure of the context. Taken on its own, the above statement is less than accurate. OO has many defining traits such as encapsulation, inheritance, and polymorphism. However, the one trait that is present in all OO incarnations without modification is polymorphism. All the others are quite variable. For example, inheritance means very different things in different OO languages. In Smalltalk it's minor convenience, whereas in Java it is a critical necessity *because* it enables polymorphism. In C++ encapsulation boundaries are enforced by 'private' and 'protected' keywords. Other languages use those keywords in subtly different ways. Yet other languages don't have them, and don't enforce encapsulation. The bottom line for OO is that it is a technique for managing dependencies and reducing coupling; and the primary tool for achieving that is polymorphism. ----- Robert C. Martin (Uncle Bob) | email: unclebob(a)objectmentor.com Object Mentor Inc. | blog: www.butunclebob.com The Agile Transition Experts | web: www.objectmentor.com 800-338-6716 "The aim of science is not to open the door to infinite wisdom, but to set a limit to infinite error." -- Bertolt Brecht, Life of Galileo
From: Robert C. Martin on 8 Jun 2005 09:02
On Wed, 8 Jun 2005 11:50:50 +0100, Gerry Quinn <gerryq(a)DELETETHISindigo.ie> wrote: >> Polymorphism will help fold redundancies together - if any. > >It can help that. Sometimes. As 'topmind' observes, it can also trap >you somewhere you don't want to be. Polymorphism is a tool, not a solution. Topmind rails against the tool because there are cases where it doesn't work well. I, for one, am glad I have the tool. ----- Robert C. Martin (Uncle Bob) | email: unclebob(a)objectmentor.com Object Mentor Inc. | blog: www.butunclebob.com The Agile Transition Experts | web: www.objectmentor.com 800-338-6716 "The aim of science is not to open the door to infinite wisdom, but to set a limit to infinite error." -- Bertolt Brecht, Life of Galileo |