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
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