Dr. Dobb's Journal - August 2008 - (Page 49)

coordinate systems, you can do so simply by deriving from the existing coordinate hierarchy and amending the PolarArray getValue() code to deal with the new type. This would be much more awkward to do in the original system! However, specifying the polar coordinate system is still bound up directly with specifying a particular pole (because the user must create a NorthPole or a SouthPole instance). We could easily use the enum Pole as a data member for class Pole, and eliminate the NorthPole and SouthPole classes. I chose not to do this because the client code would be less readable; see Listing Six (available online). I think the second version is simply not very readable! Similarly, it’s arguable that I should not have created an AbsoluteIndex class because it was easier just to have a getValue(int) for that purpose. Lastly, I realize that the use of a dynamic_cast to perform a type-based switch is a little ugly and doesn’t have great performance. We could just as well use function overloading (getValue(NorthPole&), getValue(SouthPole&), getValue(GeographicCoordinate&), and the like) to accomplish the same thing. DDJ A polar array is a representation of numeric measurements on a globe PC l. st ge y oo nd on sl e t ki e l uou ar an Th n tw m nti of . . co sed s of . ti ry ver to ad e his th in -lint 8.0 for C/C++ Presents Bug of the Month #522 100 0 8 16 24 32 40 48 56 200 60 52 44 36 28 20 12 4 100 1 9 17 25 33 41 49 57 200 61 53 45 37 29 21 13 5 100 2 10 18 26 34 42 50 58 200 62 54 46 38 30 22 14 6 100 3 11 19 27 35 43 51 59 200 63 55 47 39 31 23 15 7 Larry, a great inventor, but a novice programmer and golfer, is attempting to automate his scoring with a special device that contains software that will call "ball_is_struck()" each time it hears the ball being struck and "new_hole()" every time a new hole is reached. But something's going wrong. His scores couldn't be that low. What's going on? Visit our web site at www.gimpel.com PC-lint for C/C++ will catch this and many other bugs. It will analyze a mixed suite of C and C++ modules to uncover bugs, glitches, quirks and inconsistencies. Not your Grandpa’s lint: PC-lint has introduced several spectacular and revolutionary innovations in the art of static program analysis. Taking clues from initializers, assignments, and conditionals, variable and member values are tracked, enabling reports on potential uses of null pointers and out-of-bounds subscripts. New with Version 8: Interfunction value tracking – Actual argument values are used to initialize parameters; return values are computed; a multipass operation (you control the number of passes) allows you to plumb the depths of function behavior to arbitrary levels. Plus Our Traditional C/C++ Warnings: Uninitialized variables, inherited non-virtual destructors, strong type mismatches,ill-formed macros, inadvertent name-hiding, suspicious expressions, etc., etc. Full Language Support for ANSI/ISO C and C++. int scores[19]; int hole = 0; bool done = false; void increment( int *p ) { *p++; } void ball_is_struck() { increment( &scores[hole] ); } void new_hole() { if( hole == 18 ) done = true; else increment( &hole ); } PC-lint for C/C++ Numerous compilers/ libraries supported. Runs on Windows, MS-DOS, and OS/2. $239 FlexeLint for C/C++ The same great product for other operating systems. Runs on all UNIX systems, VMS, mainframes, etc. Distributed in shrouded C source form. Call for pricing. 30 Day Money Back Guarantee Gimpel Software Serving the C/C++ Community for 22 Years. Table 2: A great circle representation of a globe. CALL TODAY (610) 584-4261 Or FAX (610) 584-4266 www.gimpel.com PC-lint and FlexeLint are trademarks of Gimpel Software August 2008 l www.ddj.com l Dr. Dobb’s Journal 49 http://www.gimpel.com http://www.gimpel.com http://www.gimpel.com http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - August 2008

Dr. Dobb's Journal - August 2008 Contents Friday Night Fish Fry Alia Vox Developer Diaries Developer’s Notebook A Conversation with Christos Papadimitriou OpenGL and Mobile Devices: Round 2 Ellipse Specification Using Vectors Embed Custom GUIs in WPF Building RIAs on J2EE Foundations Disentangling Concepts in Object-Oriented Systems The Agile Edge Effective Concurrency Swaine’s Flames

Dr. Dobb's Journal - August 2008

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