Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1992
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1992

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Dot[]->1

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: Re: Dot[]->1
  • From: a_rubin at dsg4.dse.beckman.com (arthur rubin)
  • Date: Fri, 7 Aug 92 07:36:35 PDT

trott at physik.th-ilmenau.de (Trott Michael) writes:

 Hi mathgroup,

 On simplifying some large expressions via some rules I ended with
 expressions of the following type:

 Dot[]+Dot[x,y] .
 In this expression I would like to replace the first part by 1. So I tried:

 (Dot[] + Dot[x,y])/.{Dot[]->1}.

 But the result was not what I expected (1+x.y), but rather

 1 + 1.x.y   .
 
 Can somebody tell me how to do my disired replacement and what happens
 in the described example?
----------------------------------------------------------------------------
Dot has the attribute "Flat", so that Dot[].x = x; I think the best way to
fix it would be to use:

X_Dot :> If[Length[X]===0,1,X]

Not elegant, but it works.





  • Prev by Date: Re: Sorting of pairs
  • Next by Date: computer algebra systems are mentioned in a sf novel
  • Previous by thread: Re: Sorting of pairs
  • Next by thread: Re: Dot[]->1