Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!sgi!mtoy@xman.SGI.COM
From: mtoy@xman.SGI.COM (Michael Toy -- The S.G.I. XMAN)
Newsgroups: comp.lang.c++
Subject: Re: matrix types and [] overloading
Summary: sample implementation with a paramterized type
Keywords: matrix, [] overloading
Message-ID: <20863@sgi.SGI.COM>
Date: 21 Oct 88 02:59:20 GMT
References: <5181@saturn.ucsc.edu>
Sender: daemon@sgi.SGI.COM
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 45

In article <5181@saturn.ucsc.edu>, (Robert Skinner) writes:
> I'm constructing a general 2d Matrix object for a class I'm now taking
> on matrix computations.  It would be nice if I could
> overload the [] operator  ...
> 

--------------------------- File Matrix.h --------------------------------
//
// Generic class for 2D matrices of any type with runtime sizing
//

#define MatrixDeclare(type) \
class MatrixOf/**/type {\
    type* data;\
    int ncols; \
    public:\
    MatrixOf/**/type() \
	{ data = 0; } \
    MatrixOf/**/type(int rows, int cols) \
	{ ncols = cols; data = new type[rows * cols]; } \
    type* operator[](int row)\
	{ return data + row*ncols; }\
    ~MatrixOf/**/type()\
	{ if (data) delete data; }\
}

#define Matrix(type) MatrixOf/**/type

--------------------------- End File main.c++ --------------------------------

To define a type for a matrix of "FROB"'s, just do:

#include	"Matrix.h"

MatrixDeclare(FROB)

To get a m by n matrix of FROBS do:

    Matrix(FROB) my_matrix(m, n);

now both "my_frob = my_matrix[2][3]" and "my_matrix[2][3] = my_frob"
should work.
--
                 From the mixed up files of Mr. Michael C. Toy
Internet: mtoy@SGI.COM              UUCP: {ames,ucbvax,decwrl,sun,parcvax}!mtoy