Embedded Systems Design - June 2008 - (Page 20)

programmer’s toolbox Listing 4 Stream I/O until the next column. There’s a reason for that: it’s because I’ll be making three changes to the ﬁle structure that should make things easier in the future. I want to com// Stream I/O functions ostream& operator <<(ostream &os, Matrix plete those changes before pressing on with more func&a) tions in the class. { First, note that, in several places, I’ve used calls to the for(size_t i=0; i<a.m; ++i) { functions vClear and vCopy. These functions are found for(size_t j=0; j<a.n; ++j) in the ﬁle SimpleVec.cpp. That ﬁle was originally written cout << a.p[a.n*i+j] << ‘ ‘; to do low-level vector operations. However, they also cout < >(istream &is, Matrix vAdd and vSub, as well. &a) I could, but I’m not going to. While I don’t absolutely { for(size_t i=0; i > a.p[i]; mSub, and so forth, I also don’t pay much of a penalty to do return is; so. Most of the functions contain only one or two exe} cutable instructions, so it’s not as though I’ll be wasting lots of RAM space. There’s another thing. Although the low-level matrix functions I’ve mentioned will be identical to those for vectors, many others will be decidedly different. These include should probably be deferred to cases where we have spethe generation of scalar matrices, the product algorithms, ciﬁc uses, and therefore speciﬁc formats, in mind. For the inversion algorithm, and others. hints, you might check the I/O formats used in MATLAB. Accordingly, I’ve decided to write another collection I will call your attention to the indexing construct in of functions parallelling those in operator <<( ). It’s the same as used in function Cell( ). In truth, My shame in admitting the SimpleVec.cpp. I’d call it SimI might have been well-advised to error is well worth it if it pleMat.cpp, except for the next use that function. I blushingly admit change. drives home the point that that I made an error in the indexWith the introduction of Siming—an error that cost me an afterthe indexing math is best pleMat.cpp and its header ﬁle, I’m noon or so to ﬁnd. I had used the to eight be includhidden well down inside up in every ﬁles that muststarting to column size parameter instead of ed build. This is software written for the the row parameter, incurring an erget excessive. I’ve done things this ror that only showed up when the way in the past and never had much purpose. matrix was non-square. of a problem, but I can’t say as much There could be no better way to for other users of my software. They make the point. My shame in admitting the error is well tended to have problems collecting up all the needed ﬁles. worth it if it drives home the point that the indexing math You might also remember that I didn’t include, in this is best hidden well down inside software written for the month’s effort, any operations that involved both matrices purpose. To sprinkle such code through a main program is and vectors. Since almost everything we do with an invitation to disaster. It only takes one mis-written invector/matrix math involves both types, we’re going to stance to make your life miserable. have to make allowances for those operations, and we should do so very soon. In practice, this means adding refTHINGS TO COME erences to vectors in class Matrix, and possibly the other As usual, I’m uploading the code for the class Matrix and way round as well. To clean things up, I’ve decided to combine all the its test driver, to the web site. Check the test driver for excode—the classes Vector and Matrix, plus the low-level amples of how to use the new functions. I’ve included tests for the stream I/O. However, remem- routines in SimpleVec/SimpleMat, into a single ﬁle, plus ber that my usual test approach is silent, in the sense that it its corresponding header ﬁle. This will make the ﬁle a good gives no output unless something goes wrong. Therefore, in bit larger than I’m comfortable with, but it won’t use much the default form of the test driver, the tests of the I/O funccode space because the individual functions are so tiny. tions are commented out. Look for those changes, coming soon to a magazine You may have noticed that I’ve deferred a lot of items near you. ■ 20 JUNE 2008 | embedded systems design | www.embedded.com http://www.embedded.com

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Embedded Systems Design - June 2008 Contents #Include Party Bit Programmer's Toolbox Cover Feature: Virtual Hardware Platforms for Embedded Software Validation Allocating Memory in MATLAB-to-C Code MDD and IDEs: Making the Twain Meet in Embedded Systems Design Avoid a Thrashing Guest Editor Advertising Index Break Points Marketplace

Embedded Systems Design - June 2008

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