Polymorphism sucks [Was: Paradigms which way to go?]
in [OOP]
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From: topmind on 20 Jun 2005 12:41 > > >I have a question of you. If for the sake of argument > >the changes *are* > >random, do you still think polymorphism would simplify changes? > > Yes, because polymorphism help me to decouple. Decoupled modules are > easier to change. > First of all, I thought you agreed that not all coupling is bad (remember the suitcase analogy?). Thus less coupling is not inherantly good or bad. Your line of reasoning appears inconsistent on this. It seems coupling is "good" if it helps simplify changes, and "bad" if it does not. But this gets back to probabilities of possible change patterns. Copy-and-paste actually *reduces* coupling because it lets things be independent, for example. Thus, if reducing coupling is always good, then copy-and-paste is always good. So, let's focus on change impact. Can you answer in terms of change impact instead of "coupling"? That would be helpful. If you would rather stick to "coupling", then first we need to clarify what kind of coupling is good and what kind is bad. How about we explore a code change scenario. I have five case statement items (occuring once) and you use polymorphism instead. Now suppose the change is that the items become non-mutually exclusive (yep, that word again). Do you claim the total change effort for poly will be less than what it would be for the case statement? Somewhere around here I think I gave an example of a device driver-like thingy that now wants to output in multiple formats (HTML, PDF, RTF, etc.) in one shot so that users can browse in a file directory and pick the format they want. Remember, this was not a requirement on the first round of coding. -T-
From: Juancarlo Añez on 20 Jun 2005 12:48 Robert, (Bob?) >Of course they describe the whole things as approaching programming >from a different perspective -- and that's a fair comment. It is *much more* than a "fair comment". It is what it's all about! There's a quote from Dijsktra (that I can't find right now) in which he said to the likes of "I build languages over languages over languages until I arrive at one in which it is easy to write a solution to the problem at hand" (I read the quote in "Anatomy of Lisp" by John Allen, which I can't find right now). If you're defending that OO is a small step from function tables implementation-wise, I could not argue that. But what matters is that OO (from Simula onwards), whichever the implementation (a dynamic language may choose maps instead of vectors) was a huge conceptual step respect how we approach problem solving with programming. As big as Dijsktra's proving structured programing was complete. As big as Hoare's concept of "monitor", which provided a new insight into parallel programming (who cares if you need one, two, or three of Dijstra's "semaphores" to implementa a monitor?) It is all machine code, bits, and transistors in the end, but that is not what it's all about. For example, portable, compiled-to-byte-code languages is a very old idea that has became mainstream only recently, after people found ways to implement them efficiently. Byte-code is now much more than a convenience: it is a resource that enables designs that one would not had risked imagine just a while ago. The way we approach software analysis and design today is fundamentally different because of the availability of OO. The difference is not limited to "programming convenience". It is an epistemological kind of thing (as in Hoare and Dijsktra), absolutely. Sorry for the long note, but.... Juanco
From: Isaac Gouy on 20 Jun 2005 13:52 Robert C. Martin wrote: > On 20 Jun 2005 02:16:36 -0700, ggroups(a)bigfoot.com wrote: > > >Of course, the words of the creators of Simula will be of no comfort > >to prevaricators who cannot deal with the fact that OO did not appear > >from some programmers hacking around with Algol-60 and discovering > >things by mistake (a s/w Penicillin in effect) ... *** > > Steve, there is a difference between accusing someone of being > incorrect, and accusing someone of being a liar. The first is > civilized, and the second is libelous. Robert, I was puzzled by your reaction (in English prevaricate is not a synonym for lie) - so after checking the OED, I looked in Websters and found the definition I expected "to turn aside from, or evade, the truth; equivocate" and then a secondary meaning "to tell an untruth". Maybe something was lost in translation between English and American.
From: coeval on 20 Jun 2005 19:44 Years ago I've already come across this question; how to apply objects polymorphism at the business level? At that time due to the buzzword running by all OO methodologies it was hard to find other people asking the same question. So I decided to a look at some formal methods (Z, VDM) to find a formal, mathematical definition about objects polymorphism..... and methodologists were stuck to demonstrate a logical proof. As far I remember just one book, (K. Lano from the Imperial College of London ), quoted , just at the beginning : " We are unable to give you any formal description about the polymorphism because it has not mathematical proof". Since that time I only use polymorphism " for animal, shape and devices". When one says the main concept in OO is polymorphism, let me I have some doubts. I read lot of books about OO to improve my skills but most of the time the real world is completely different. I suggest OO authors and OO evangelists should dive in 100,000 lines of Java/C++ code, written by numerous OO-ish programmers, to fix bugs, defects, performance issues and misconceptions. And I've learned by myself how is hard to add/change huge number of line code based on just class-inheritance technique "baked" elsewhere. In the same time I started using OMT/UML to design my project but years after years as I used and I am still using relational databases I changed my way because I want to explain to my customer what I really understand about its business. So I am now using NIAM and ORM methods ( Objects relational modelling from Terry Halpin North Face University) that are well-suited for relational databases. Harvey
From: Phlip on 21 Jun 2005 00:24
coeval wrote: > When one says the main concept in OO is polymorphism, let me I have > some doubts. Have you read the book /Design Patterns/? The authors held themselves to the laudable goal of citing 3 real-life projects per pattern. Each had more, of course. > I read lot of books about OO to improve my skills but most of the time > the real world is completely different. The "real world" is the problem. Plenty of OO tutorials accidentally start with "OO works best because you can model the real world", or similar. This is heinous verbiage for one simple reason: If we discuss which of two OO models is better, saying "mine is better because it models the real world" adds nothing to the conversation. The OO model with the simplest implementation and least redundancy is better. The Real World _never_ obeys that guideline. But sometimes the best way to replace redundancies with flexibilities is with virtual methods. You use OO every time you open a file handle and write to it. The target could be a disk file, a console, a printer, etc. That's polymorphic behavior encapsulated behind an interface: OO. > I suggest OO authors and OO evangelists should dive in 100,000 lines of > Java/C++ code, written by numerous OO-ish programmers, to fix bugs, > defects, performance issues and misconceptions. Show me a technology that can't be abused and I'l show you one that's useless. -- Phlip http://www.c2.com/cgi/wiki?ZeekLand |