Robert Dodier wrote:
> On Mon, Mar 24, 2008 at 9:45 AM, Raymond Toy (RT/EUS)
> <raymond.toy at ericsson.com> wrote:
>
>
>> While playing with donlp2, I noticed that maxima orders vector variables
>> in "reverse" order. For example,
>>
>> sum(x[k],k,1,5) -> x[5]+x[4]+x[3]+x[2]+x[1].
>>
>> While I usually just accept whatever order maxima wants to display
>> variables, this particular example seems wrong. There's a natural
>> ordering and it's by the index of the variable.
>>
>> Any reason why it should be in reverse order? Any objections to
>> changing it for this case? (I don't know if that's really possible or
>> not. I haven't looked.)
>>
>
> The terms x[1], x[2], ... are stored in order of increasing index.
> Whether they are displayed that way or reversed is controlled
> by the global variable powerdisp. When powerdisp=true the terms
> are displayed in order of increasing index.
>
> I'm not opposed to changing the default value of powerdisp to true.
>
> Aside from changing powerdisp, we could also change GREAT
> (the function which implements Maxima's idea of canonical
> ordering). Changing GREAT could have rippling effects, though.
>
> FWIW
>
> Robert Dodier
> _______________________________________________
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> Maxima at math.utexas.edu
> http://www.math.utexas.edu/mailman/listinfo/maxima
>
>
For those of us who already have routines which make use of the current
ordering of variables, e.g. as in
%i1) p: x^2 + y^2 - x*y;
2 2
(%o1) y - x y + x
changing some defaults would create havoc and, perhaps, cause a lot more
time spent modifying existing debugged code.
If it is only a matter of setting a flag to be 'true' or 'false' in new
code, why not leave the defaults as they are?
-sen