Hi all, I have been looking into this critical bug
http://trac.sagemath.org/sage_trac/ticket/6376 (This bug affects me badly and in fact I need to use sage-3.4 for my own work to avoid this) This bug is related with "D" <-> "diff" conversion for symbolic functions. Following are my observations and a proposal to deal with this bug. [o] D <-> diff conversion is NOT one-to-one Ex: (A) diff( f(x-a), x) => D[0] f(x-a) (B) D[0](f)(x-a ) => (i) diff( f(x-a), x) (ii) - diff( f(x-a), a) So conversion is tricky. Here are my proposals to deal with this: (1) Keep current conversion when arguments are all symbolic variables. This way solving differential eqn and others will work as usual via maxima. (2) Do not convert D to diff format when an argument is an expression. In that case pass it to maxima as another symbolic function of the form D( f(x-a), [0] ) From maxima output, we can then convert it back to D format. (3) Finally, let's represent (text-mode) D derivative as D( f(x,y), [0,0,1] ) ( which is represented now as D[0,0,1](f)(x,y) ) or optionally D( f(x,y), [(0,2), (1,1)] ) This form has several advantages: (i) Above is a valid form of python function and one can copy-paste sage output from one cell to another as vaild sage input. Currently this is not the case. (ii) Sage output often contains terms like "D[0](f)(g(x))". However, right now there is no way one can enter above in Sage directly. I will be happy to implement this if we can reach consensus. Cheers, Golam --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
