>> From: Richard Patterson "rpatters"
I want to define differential operators and test them on
a polynomial f(x,y):
f:=(x,y)->a*x^2+b*x*y+d*y^2;
2 2
f := (x, y) -> a x + b x y + d y
If the differential operator has constant coefficients
> op1:=2*D[1]+3*D[2];
op1 := 2 D[1] + 3 D[2]
then everything works fine:
> op1(f)(x,y);
4 a x + 2 b y + 3 b x + 6 d y
How do I accomplish the same thing if the coefficients are
unspecified constants?
> op2:=c*D[1]+d*D[2];
op2 := c D[1] + d D[2]
> op2(f)(x,y);
c(f)(x, y) (2 a x + b y) + d(f)(x, y) (b x + 2 d y)
It was no help to include
> assume(c,constant): assume(d,constant):
> op2(f)(x,y);
c~(f)(x, y) (2 a x + b y) + d~(f)(x, y) (b x + 2 d~ y)
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(NAG)
