[Maxima] how do I use upper indicies in Maxima?
Andrey G. Grozin
A.G.Grozin at inp.nsk.su
Thu May 17 09:42:23 CDT 2007
On Thu, 17 May 2007, Vadim wrote:
> in TexMacs when I do
> I see small greek letter alpha with lower index zero.
I think you should distinguish computations in the maxima language and
typesetting (though front-ends like TeXmacs try to minimize the
difference, it never actually disappear). While you are doing computations
and maxima programming, don't bother too much about typesetting; when you
fine-tune typesetting for a final publication, don't do computations.
I particular, alpha is not a variable, from the point of view of maxima
language. It is an array reference to which no value has been assigned. In
most cases, it can be used just like a variable, but not always. So, when
you need a programming variable, use a variable, alpha0 for example; when
you need an array, use an array; and how they are displayed on the screen
is less important than the correctness of the program.
> 1. How do I specify *upper* indicies?
No way. The TeXmacs-maxima interface tries to ensure that the output can
be cut-and-pasted into an input; an upper index would be interpreted as
raising to a power.
Tensor packages have their own concept of upper and lower indices. There
are some functions to display tensor expressions with indices. If you want
tensors, use one of the tensor packages available in maxima.
> 2. Yet, how do I specify several indicies at once? "alpha[ij]; " isn't
> what I want, because it refers to ij, but specifying coma looks
> confusing (IMHO)
Again, I think your aethetical considerations interfere with the syntax of
the maxima programming language here. If you need an array with 2 indices,
use an array: alpha[i,j]. If you need a variable, use a variable: alphaij
or alpha_i_j or whatever.
> 3. why I need to use %gamma to use small greek gamma, but small greek
> alpha designated as "aplha". Could this inconsistency factored out
> somehow? (by undefining another gamma definition?)
%pi and %gamma are special, they have a fixed meaning: %pi is obvious;
%gamma is the Euler constant. They cannot be used for any other purpose.
The reason is following: in the output, it is convenient to write the
constants %pi and %gamma as the greek letters; output should be copyable
to input; this means that the greek letters pi and gamma should be
interpreted as the mathematical constants %pi and %gamma.
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