Well, that's most annoying if it's a bug in FriCAS. I might try the same thing in Axiom and see what happens.
I'll let you know tomorrow (it's nearly midnight in Melbourne, Australia right now). -A. On Monday, January 20, 2014 10:49:00 PM UTC+11, Ralf Hemmecke wrote: > > On 01/20/2014 12:19 PM, Alasdair wrote: > > Try this: > > Thanks... I've shortened it a bit and somehow believe that must be a bug. > > )cl completely > f:=operator 'f > y:=operator 'y > f1:=D(f(x,y(x)),x) > f2:=D(f1,x) > f3:=D(f2,x) > kxy:=eval(D(f(x,z),[x,z]),z=y(x)) > > In the end I get... > > f3:=D(f2,x) > > > (5) > ,,, , 3 > f (x,y(x)) + f (x,y(x))y (x) + y (x) f (x,y(x)) > ,1,1,1 ,2 ,2,2,2 > + > , 2 , , 2 > y (x) f (x,y(x)) + y (x)f (x,y(x)) + y (x) f (x,y(x)) > ,2,2,1 ,2,1,1 ,2,1,2 > + > , , 2 , > y (x)f (x,y(x)) + y (x) f (x,y(x)) + y (x)f (x,y(x)) > ,1,1,2 ,1,2,2 ,1,2,1 > + > , > ,, > (3y (x)f (x,y(x)) + f (x,y(x)) + f (x,%B) + f > (x,y(x)))y (x) > ,2,2 ,2,1 ,2,1 ,1,2 > Type: > Expression(Integer) > kxy:=eval(D(f(x,z),[x,z]),z=y(x)) > > > (6) f (%A,y(x)) > ,1,2 > Type: > Expression(Integer) > > That looks to me like even two bugs. Why would evaluating f3:=D(f2,x) > have influence on kxy:=eval(D(f(x,z),[x,z]),z=y(x))? Note that the > ordinary result should be like this: > > (7) -> )cl completely > All user variables and function definitions have been cleared. > All )browse facility databases have been cleared. > Internally cached functions and constructors have been cleared. > )clear completely is finished. > (1) -> f:=operator 'f > > (1) f > Type: > BasicOperator > (2) -> y:=operator 'y > > (2) y > Type: > BasicOperator > (3) -> kxy:=eval(D(f(x,z),[x,z]),z=y(x)) > > (3) f (x,y(x)) > ,1,2 > Type: > Expression(Integer) > > But I guess that is a follow-up error from the computation of > f3:=D(f2,x). Also there I wouldn't want to see %B to appear in the output. > > I faintly remember that Waldek introduced that local variables to > indicate "derivation wrt the n-th variable", because there was a bug for > another expression. Looks to me like this code must be revisited. > > But I'm somehow clueless why evaluation of D(f2,x) leads to a side effect. > > Ralf > > -- 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 post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/fricas-devel. For more options, visit https://groups.google.com/groups/opt_out.
