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MathGroup Archive 2005

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Re: D[...] change in 5.1

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58706] Re: D[...] change in 5.1
  • From: Alexei Akolzin <akolzine at uiuc.edu>
  • Date: Fri, 15 Jul 2005 03:02:22 -0400 (EDT)
  • Organization: University of Illinois at Urbana-Champaign
  • References: <db57qa$4ri$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

I am sorry, here what I meant:

In[1] := n /: D[n[i_], x[j_], NonConstants -> n] := (1/r)*(d[i, j] - 
n[i]*n[j]);

In[2] := D[n[k], x[l], NonConstants -> n]
Out[2] = (d[k, l] - n[k] n[l]) / r

In[3] := D[1 + n[k], x[l], NonConstants -> n]
Out[3] = D[n, x[l], NonConstants -> n]

In[4] := $Version
Out[4] = "5.1 for Linux x86 (64 bit) (January 27, 2005)"

From my point of view Out[3] should be exactly equal to Out[2]. It was 
in earlier versions, but it is not in 5.1! The difference gives all 
kind of problems in more complicated expressions. I try to combat this 
with Hold and ReleaseHold, but ran into a more peculiar problem, which 
is even more puzzling to me:

In[1] := n /: D[ n[i_], x[j_], NonConstants -> {n, r} ] := ( \[Delta][i, 
j] - n[i] n[j]) / r;
In[2] := r /: D[ r, x[i_], NonConstants -> {n,r} ] := n[i];

In[3] := D[ \[Delta][i,j] BesselJ[0 , k r] , x[l], NonConstants -> 
{n,r} ]
Out[3] = 0

In[4] := D[ \[Delta][i,j] BesselJ[0 , k r] , x[m], NonConstants -> 
{n,r} ]
Out[4] = - k BesselJ[1,k r] n[m] \[Delta][i,j]

In[8] := ?k
Global`k

In[9]:= ? \[Delta]
Global`\[Delta]

Now, Out[3] and Out[4] should be the simmilar. The only difference is 
what simbol "m"  or "l" is used in respective differentiation by x[m] 
or x[l]. But again they are not. The problem disappears if I substitute 
"\[Delta]", which I enter from keyboard as Esc d Esc, for example by 
"d".

Sincerely,
Alexei.


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