Thank you! The trouble is that my above output seems related to something else:
)cl all > f:=operator 'f > y:=operator 'y > kxy:=eval(D(f(x,z),[x,z]),z=y(x)) > produces f[,1,2](x,y(x)) > which is what I want. So there must be something else I'm doing which causes the above "%A" to appear. But after a few more similar commands, when I entered the command for kxy again, the pesky %A turns up. I know, from my previous work with finite fields, how FriCAS uses %A, %B etc for indeterminate variables (such as the variables for the formal polynomials which form a Galois field), but apparently - according to the Jenks/Sutor book - they are only for display. So there must be some internal representation for kxy which will allow me to substitute for it... Thanks, Alasdair On Monday, January 20, 2014 8:22:52 PM UTC+11, Ralf Hemmecke wrote: > > On 01/20/2014 09:31 AM, Alasdair wrote: > > My input: > > > > f:=operator 'f > >> y:=operator 'y > >> kxy:=eval(D(f(x,z),[x,z]),z=y(x)) -- <- thanks to Waldek for this idea > >> > > > > The output: > > > > f[,1,2](%A,y(x)) > >> > > > > Why is there this "%A" all of a sudden, instead of "x"? I'm trying to do > > some pattern matching (well, substitution), and this sort of thing is > very > > unhelpful! > > Maybe the following helps. > > (1) -> f := operator 'f > > (1) f > Type: > BasicOperator > (2) -> y := operator 'y > > (2) y > Type: > BasicOperator > (3) -> dxz := D(f(x,z),[x,z]) > > (3) f (x,z) > ,1,2 > Type: > Expression(Integer) > (4) -> kxz := kernels(dxz).1 > > (4) f (x,z) > ,1,2 > Type: > Kernel(Expression(Integer)) > (5) -> operator kxz > > (5) %diff > Type: > BasicOperator > (6) -> argument kxz > > (6) [f (x,%C),%C,z] > ,1 > Type: > List(Expression(Integer)) > > The kernel stores what it is composed from. It's a %diff of > > f (x,%C) > ,1 > > with respect to the variable %C (second variable) and %C is in the end > renamed to z. Just imagine that it would have been a z in the first > argument. Note that D(..., [x,z]) is the partial derivative. > > 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.
