crossprd.src

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/*
** crossprd.src
** (C) Copyright 1988-1998 by Aptech Systems, Inc.
** All Rights Reserved.
**
** This Software Product is PROPRIETARY SOURCE CODE OF APTECH
** SYSTEMS, INC.    This File Header must accompany all files using
** any portion, in whole or in part, of this Source Code.   In
** addition, the right to create such files is strictly limited by
** Section 2.A. of the GAUSS Applications License Agreement
** accompanying this Software Product.
**
** If you wish to distribute any portion of the proprietary Source
** Code, in whole or in part, you must first obtain written
** permission from Aptech Systems.
**
**> crossprd
**
**  Purpose:    Computes the cross products (vector products) of
**              sets of 3x1 vectors.
**
**  Format:     z = crossprd(x,y);
**
**  Input:      x    3xK matrix, each column is treated as a 3x1 vector.
**
**              y    3xK matrix, each column is treated as a 3x1 vector.
**
**  Output:     z    3xK matrix, each column is the cross product
**                   (sometimes called vector product) of the
**                   corresponding columns of x and y.
**
**  Remarks:    The cross product vector (z) is orthogonal to both x and y.
**              sumc(x.*z) and sumc(y.*z) will be Kx1 vectors all of whose
**              elements are 0 (except for rounding error).
**
**  Globals:    None
*/

proc crossprd(x,y);
    local r1, r2, r3;
    r1 = x[2,.].*y[3,.]-x[3,.].*y[2,.];
    r2 = x[3,.].*y[1,.]-x[1,.].*y[3,.];
    r3 = x[1,.].*y[2,.]-x[2,.].*y[1,.];
    retp( r1|r2|r3 );
endp;