Powerdisp is intended for the display of power series. If it works for
anything else, it would be mildly surprising. In fact, if it works for
a particular problem involving power series not in canonical truncated
taylor series form, that is, itself, mildly surprising.
(I think I incorporated this feature into Macsyma circa 1970.)
RJF
Robert Dodier wrote:
>On 10/5/07, Stavros Macrakis <macrakis at alum.mit.edu> wrote:
>
>
>
>>On 10/5/07, van Nek <van.nek at arcor.de> wrote:
>>
>>
>>>Is it possible to have a+b => a+b as the default (without calling ordergreat)?
>>>
>>>
>
>Yes. The ordering of terms for display of a literal sum is
>controlled by the global variable powerdisp.
>
>(%i2) powerdisp;
>(%o2) false
>(%i3) c + x + 1 + b + a + x^3 + x^2;
>(%o3) x^3+x^2+x+c+b+a+1
>(%i4) powerdisp : true;
>(%o4) true
>(%i5) c + x + 1 + b + a + x^3 + x^2;
>(%o5) 1+a+b+c+x+x^2+x^3
>
>We could consider making powerdisp = true the default.
>Or just cut out the stuff in FORM-MPLUS which reverses the
>order of the arguments from the order in which they're stored.
>
>
>
>>I believe that the motivation for the current ordering (reverse
>>alphabetical in sums, alphabetical in products) is that letters at the
>>end of the alphabet (x,y,z) often represent variables, while letters
>>at the beginning of the alphabet (a,b,c) often represent constants or
>>parameters. Users probably want to see
>>
>> c*x^3 + b*x + a
>>
>>rather than
>>
>> a + x*b + x^3*c
>>
>>
>
>Better still is a + b*x + c*x^3, which is achieved by powerdisp : true
>or equivalent modification of FORM-MPLUS.
>
>
>
>>We could of course define pretty much any order we wanted. For
>>example, we could decide on the order w,x,y,z / p,q,r,s,...u,v /
>>a,b,...o.
>>
>>
>
>I don't think we need to invent a new ordering policy.
>We just need to get the display code to behave differently.
>
>FWIW
>
>Robert
>_______________________________________________
>Maxima mailing list
>Maxima at math.utexas.edu
>http://www.math.utexas.edu/mailman/listinfo/maxima
>
>