In article <87sir2et1d....@elektro.pacujo.net>, Marko Rauhamaa <ma...@pacujo.net> wrote: >Mark Lawrence <breamore...@yahoo.co.uk>: > >> http://c2.com/cgi/wiki?SwitchStatementsSmell > >Your brief summary, please, Mark? > >Anyway, the first 1000 lines or so that I managed to read from that page >stated a valid principle, which however doesn't invalidate the existence >of a switch statement. > >A colleague of mine taught me decades back that the whole point of OO >was the avoidance of if and switch statements. So if your code has an if >or switch statement, chances are you are doing something wrong. > >I agree. > >However, like all other maxims, that principle, too, has exceptions. Two >recurring examples are parsers/decoders and state machines. Sure, you >can implement states beautifully with objects/classes (and I do do that >when performance is not an issue), but having experimented with >different implementation techniques (in C, C++ and Java), I have >concluded that switch statements are often unbeatable in performance and >clarity.
I can't see why parsers decoders are any different. The Pentium assembler in my ciforth's ``forth.lab'' library has not a single if statement and I reckon it is a superior design. (State is kept in an ai blackboard fashion in bitmaps.) Forth has of course a built in "look it up, then execute it", which could be regarded as a giant switch. > >And I sometimes run into convoluted factory (anti)patterns whose sole >purpose is to avoid straightforward switch statements in a decoder. > > >Marko -- Albert van der Horst, UTRECHT,THE NETHERLANDS Economic growth -- being exponential -- ultimately falters. albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst -- https://mail.python.org/mailman/listinfo/python-list
