[Maxima-discuss] iterated at(..)

[Andrei Z. <zoa...@gm...>]

Helo, group!
Let us consider the code:
kill(all);
eq: φ(s) = q(s+λ-λ*φ(s));
gradef(q(s), q1(s))$
atvalue(q(s), [s=0], 1)$ atvalue(q1(s), [s=0], -m)$
atvalue(φ(s), [s=0], 1)$ atvalue(diff(φ(s),s), [s=0], -Mz)$
diff(eq, s, 1);
at(%, [s=0]);
fin: at(%, [s=0]);
fin1: solve(fin, Mz);

By trial-and-error, the second call to at(...) is needed here,  the first
one returns an answer with q1(0) in it. Why can't at(...) find a fixed
point itself?
Can somebody explain this behaviour?

Thanks in advance,
 Andrei Zorine

p.s. This is a partial code from my class, we studied  Laplace transform
for a busy period if it matters....