This thread now contains some examples of how different computer algebra systems handle the chain rule. The following might help in sage <-> maxima communication:
By default, maxima leaves an expression: "diff( f(g(a,b,c),u,v), a)" untouched. But maxima can in fact represent the result from applying the chain rule to this expression using its "at" function: at( diff (f (x1,x2,x3),x1), [x1=g(a,b,c),x2=u,x3=v])*diff(g (a,b,c),a); Using this trick, it should be pretty straightforward to encode sage's "D" notation into something that is at least valid maxima syntax. The only problem is guessing how many formal parameters are needed, but by the time a "D[i](f)" is encountered as an operator, its "operands" list should be known. Alternatively, many symbolic variables declare how many variables they expect. Parsing it back might be a little more elaborate, but if all else fails, we can do that via generic subexpression substitution. Given that we'll have to have a routine that parses "D[i]" differential expressions into "diff and at" expressions to communicate with maxima, we could use that same routine to produce a latex representation as well. Maxima's 2d prettyprinter tries it, with mixed results. The main difficulty for printing would be to come up with reasonable names for the intermediate variables (note that the x1,x2,x3 above had to be invented). This would give a route that is slightly different from the route proposed in the patch 6756. It would only affect the printing of differential expressions and not add an alternative internal representation of derivatives. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
