How to order variables in Maxima?

问题

I want to give variables a specific order in an equation in Maxima. This is display purposes only.

For example:

(%i1) E=(h*c)/%lambda;
                                c h
(%o1)                     E = -------
                              %lambda

I want the h and c variables to be in that order when displayed. I looked at ratvars() and ordergreat() but they don't appear to be relevant here.

Thanks for your help.

回答1:

It appears that declare(<var>, mainvar) was what I was looking for. When mainvar attribute is declared for a variable it "succeeds all other constants and variables".

I was trying this using the STACK plugin for Moodle. I needed to remove the mainvar keyword from the forbidden list in the file casstring.class.php.

回答2:

Actually, I think ordergreat() is the function you need, maybe you did a sorting before that needed unorder() first ro reset things. Try

unorder()$ ordergreat (h, c)$ E=(h*c)/%lambda; 

and

unorder()$ ordergreat (c, h)$ E=(h*c)/%lambda;

来源：https://stackoverflow.com/questions/36456544/how-to-order-variables-in-maxima