Re: [Maxima-discuss] Encoding of bold, underscored, subscripted and superscripted identifiers by wxmaxima

[Michel T. <ta...@lp...>]

Le 16/12/2015 06:13, Gunter Königsmann a écrit :
> wxMaxima has autocompletion: Ctrl+Tab autocompletes a command, Shift+Ctrl+Tab shows its parameters.

At least with the version of wxmaxima which come with my LTS version of 
Ubuntu, these commands do nothing (in fact insert a Tab). I have other 
problems, for example Ctl-C Ctl-V don't work properly between wxmaxima
and other windows, etc. Some menu entries crash the program.
I am under the impression that wxmaxima is mainly tested under Microsoft 
Windows, and probably Mac OS, but free operating systems are second 
class citizens.

To come back to the position of indices, i think it is ill advised to
denote x[i] as x_i when i belongs to [0-9] as seems to be the case in
this commit to wxmaxima. Indeed the index is frequently a letter and can 
be either upper or lower (covariant or contravariant). To see typical 
usage, see for example:
https://en.wikipedia.org/wiki/List_of_formulas_in_Riemannian_geometry
If you look for example at the Riemann curvature tensor R, the first 
index is upper and the three other ones are lower, R^l_{ijk}. This is a 
property of R and not of ijkl. For example the Ricci tensor is R^l_{ilj}
with implied summation on index l which appears both upper and lower 
(the so called Einstein contraction) so the position cannot be a 
property of the index, but of the main symbol R. Hence i like much 
better the proposition of Robert Dodier which describes the position of 
indices as property of the main symbol. Of course his way of describing 
this position requires much typing, which i don't like. Some abbreviated 
form like in the TeX usage would have better chance on concrete use, for 
example uddd for the R above, one could imagine
d|d for one one pre index and one post index, both down, etc.


-- 
Michel Talon