"Stavros Macrakis" <macrakis at alum.mit.edu> writes:
> On 5/9/07, Nikos Apostolakis <nikos.ap at gmail.com> wrote:
>
> I think that the "differential" del should be a linear operator, so
> that for example del(3*x) should simplify to 3*del(x).
>
>
> Where to start....
>
> del(ex) is the noun-form corresponding to diff(ex): that is, del(ex) == 'diff
> (ex). Thus you can use forms like del(x*y) to mean "the total differential of
> x*y" without having it expand to x*del(y)+y*del(x). This is intentional.
>
[...]
>
> As with other noun forms, del can be expanded out explicitly using ev( <expr>,
> del) or ev( <expr>, diff). Or you can ask Maxima to expand all noun forms in
> an expression with ev(<expr>, nouns). In the above example,
>
> f : x^2 * y^3$
> df: diff(f)$ => 3*x^2*y^2*del(y)+2*x*y^3*del(x)
> df3: subst(3*x,y,df) => 27*x^4*del(3*x)+54*x^4*del(x)
> ev(df3,del) => 135*x^4*del(x)
>
> Hope this helps,
>
Yes it was very very helpful. Thank you.
-- nea
> -s
>