Re: Odd ordering of results?

*To*: mathgroup at smc.vnet.net*Subject*: [mg99598] Re: [mg99527] Odd ordering of results?*From*: peter <plindsay.0 at gmail.com>*Date*: Fri, 8 May 2009 00:20:56 -0400 (EDT)*References*: <200905071035.GAA19398@smc.vnet.net>

is this a "set" versus "list" issue perhaps; i.e. list is ordered, set isn't ? Peter 2009/5/7 AES <siegman at stanford.edu>: > I'm evaluating an optical interferometer problem in which an input wave > e1 produces internal, reflected and transmitted waves e2 thru e7 that > are connected by the linear equations > > waveEqns = {e1 == 1, e2 == rho12 e1 + t42 e4, e3 == rho= 43 e4 + t13 e1, > e4 == gL e6, e5 == gL e3, e6 == rho56 e5, e7 == = t57 e5}; > > where the rho_nm and t_nm are reflection and transmission coefficients > and the input wave amplitude is arbitrarily set to e1==1; and then > solving these using > > waveSolns = Solve[waveEqns, {e2, e3, e4, e5, e6, e7}] > > and getting a set of rules en-><stuff> for e2 thru e7 which are ordered > in the sequence > > Out[] = {{e2 e7 e3 e6 e5 e4 }} > > with the "stuff" stripped out for brevity. > > What puzzles me -- not a problem, just curious -- is the _order_ in > which these rules appear. > > Even more puzzling: If I take out the leading "e1==1," statement i= n > waveEqns I get the same results, except each "stuff" becomes > "e1*same_stuff" -- and the set of rules produced by waveSolns is now in > the different order > > Out[] = {{e2 e7 e3 e4 e5 e6 }} > > Odd . . . (seems like the natural thing would be to order the list on > the left side of the en-><stuff> terms, getting e2 to e7 in either case) > > -- Peter Lindsay

**References**:**Odd ordering of results?***From:*AES <siegman@stanford.edu>