On 5/22/26 10:09 PM, Waldek Hebisch wrote: > > Representation of derivatives needs a dummy. Kernels may > be nested and we sometimes need to substitute for dummies. > Old code in few other places (not this one) tried to use > the same dummy and this led to obscure bugs. Those bugs > were fixed by consistently using new dummies. > > Need for distinct dummies may be unobvious and people believed > that reusing dummy is safe, but it is easy to overlook some > special case. So, I very much prefer current state, that > is consistently using new dummies. >
That code has remained the same since the beginning of FriCAS, so at least unchanged for 20 years, maybe 40 years. I believe with the introduction of encode_diff/decode_diff, this usage of new dummy is no longer needed. In encode_diff, for high order derivatives, same dummy symbols are reused. If certain rules are followed (i.e alpha substitution), then transformation of (%diff) kernel will not mess things up. For making changes safe, we can add some assertions there. - Qian -- You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/fricas-devel/06ad9fe1-a744-49c9-818f-a5347973afcd%40gmail.com.
