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<HTML><HEAD><TITLE>Newmat09 - unspecified type</TITLE></HEAD><BODY><H2>Unspecified type</H2><A HREF="cholesky.html"> next</A> - <A HREF="cholesky.html"> skip</A> - <A HREF="refer.html"> up</A> - <A HREF="index.html"> start</A><P>Skip this section on your first reading.<P>If you want to work with a matrix of unknown type, say in a function. Youcan construct a matrix of type <TT>GenericMatrix</TT>. Eg<PRE> Matrix A; ..... // put some values in A GenericMatrix GM = A;</PRE>A GenericMatrix matrix can be used anywhere where a matrix expression can beused and also on the left hand side of an <TT>=</TT>. You can pass any type ofmatrix (excluding the Crout and BandLUMatrix types)to a <TT>const GenericMatrix&</TT> argument in a function. However mostscalar functions including Nrows(), Ncols(), Type() and element access do notwork with it. Nor does the ReturnMatrix construct. See also the paragraph on<A HREF="solve.html">LinearEquationSolver</A>.<P>An alternative and less flexible approach is to use BaseMatrix orGeneralMatrix.<P>Suppose you wish to write a function which accesses a matrix of unknowntype including expressions (eg <TT>A*B</TT>). Then use a layout similar to thefollowing:<PRE> void YourFunction(BaseMatrix& X) { GeneralMatrix* gm = X.Evaluate(); // evaluate an expression // if necessary ........ // operations on *gm gm->tDelete(); // delete *gm if a temporary }</PRE>See, as an example, the definitions of <TT>operator<<</TT> in newmat9.cpp.<P>Under certain circumstances; particularly where <TT>X</TT> is to be used justonce in an expression you can leave out the <TT>Evaluate()</TT> statementand thecorresponding <TT>tDelete()</TT>. Just use <TT>X</TT> in the expression.<P>If you know YourFunction will never have to handle a formula as itsargument you could also use<PRE> void YourFunction(const GeneralMatrix& X) { ........ // operations on X }</PRE>Do not try to construct a GeneralMatrix or BaseMatrix.<P><A HREF="cholesky.html"> next</A> - <A HREF="cholesky.html"> skip</A> - <A HREF="refer.html"> up</A> - <A HREF="index.html"> start</A><P></BODY></HTML>⌨️ 快捷键说明
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