Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ihnp4!homxb!mtuxo!mtune!rutgers!im4u!ut-sally!husc6!cmcl2!brl-adm!adm!V4039%TEMPLEVM.BITNET@CUNYVM.CUNY.EDU
From: V4039%TEMPLEVM.BITNET@CUNYVM.CUNY.EDU (Stan Horwitz)
Newsgroups: comp.lang.c
Subject: Re: parens honored
Message-ID: <11205@brl-adm.ARPA>
Date: 11 Jan 88 15:23:23 GMT
Sender: news@brl-adm.ARPA
Lines: 25


  I have a suggest which allows numerical programmers to avoid using temporary
variables in their C programs.  Restructure your formula so in a way that C
has no other option but to evaluate it correctly.  This should eliminate most
but not all, of the need for temporary variables.

   EXAMPLE:  Given arrays X and Y, and XX, XY, and SSXY, the formula
             SSXY = SUM(XY)/N - SUM(X) * SUM(Y) / N where N is the number
             of elements in all of the arrays is part of the method of
             linear least squares regression.  In order to get C to see
             this formula correctly, it can be reorganized to look like
             SSXY = (-SUM(Y) * SUM(Y) + SUM(XY)) / N.  In this form, there
             can be no ambiguity (or misinterpretation) as to how the formula
             is to be computed by any compiler.  Oops, almost forgot, the
             function SUM will take an array of size N and return the sum of
             it's elements.  Don't worry about what types things are.  Just
             assume every thing is interger with the exeption of SSXY which
             could be of type float.

  This allows the evaluation of the formula with no need to computer temporary
variables.

  Stan Horwitz
  V4039 at TEMPLEVM.BITNET
  Philadelphia, PA