Directional Derivative

[salvomic]

I'm trying this program:

Code:


#cas
// Directional derivative: dot(grad(f0), normalize(v))
derivdir(f,v):=
BEGIN
local g:=grad(f,[x,y,z]);
// gradient
local w:=normalize(v);
// versor
m:=dot(g,w);
// dot product
return m;
END;
#end

It seems to works with f as a function (expression), f(0), like (x^2-x*y) and v as vector (also not normalized), like [3,4] or [x,3y]; the program first normalize the vector finding its versor, and then return the symbolic directional derivative in the direction of that vector...

Any help to make it better?
There is a way to have the function listed in the Toolbox -> User?

Thank you :-)

salvo