NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/comp/graphics/14325

Internet Message Format | 1993-01-29 | 2.2 KB

Xref: sparky comp.graphics:14325 comp.windows.x.pex:709 comp.graphics.opengl:283
Path: sparky!uunet!usna!dfr
From: [e-mail] (PROF D. Rogers (EAS FAC))
Newsgroups: comp.graphics,comp.windows.x.pex,comp.graphics.opengl
Subject: Re: Row major or column major matrices?
Message-ID: <[e-mail]>
Date: 27 Jan 93 18:36:02 GMT
References: <[e-mail]> <[e-mail]> <[e-mail]>
Sender: [e-mail]
Followup-To: comp.graphics
Organization: U. S. Naval Academy
Lines: 34

In article <[e-mail]> [e-mail] (John Scott Peter XXXIII) writes:
!Well, I eagerly await your agent of dismemberment....
!
!Actually, I have no clear preference, and I'll explain why.  In all my
!education (math and physics, B.S Physics UCLA 1986), only row-major matrices
!were used, so I naturally think of that as the standard.  However, I have an
!idea as to why so many people are switching to column-major notation.  It's
!so that matrices can be post-multiplied instead of pre-multiplied!  Post-
!multiplication notation accords better with the compound operators of C and
!C++.  If you're writing a matrix class in C++, and you want to multiply one
!matrix by another, it seems natural to define the operator `*=' as the
!multiplication operator, such that:
!
!    A *= B means A = A * B.
!
!I was writing such a class for a simple 3-D graphics program, and I quickly
!realised that the most common multiplication I wanted to do was PRE-
!multiplication.  I therefore said `Screw convention', and defined `*=' so
!that
!
!    A *= B means A = B * A.
!
!So, my solution was to change the standard C relationship between `*=' and
!`*'.  Apparently, others decided it was better to change the very operation
!of matrix multiplication to imply a column-major order, so that `A *= B'
!would still mean `A = A*B'.

To heck with C and C+ and Fortran etc. You'll should really look
at how ANSI BASIC (yes that nasty word) handles matrices. How about
like a mathematician would? Yup that's the way they do it AND
it is all built into the language! Amazing. When are these modern
langauage designers going to get with it.

Dave Rogers