I need to write in Maxima the following expression, where $f$ is a generic function of $x$ not specified:
$$ f'(e) - 1 \quad \text{or} \quad \left.\dfrac{df}{dx}\right|_{x=e}-1 $$
I'm trying to making it differentiating a general $f(x)$ and then applying the substitution of $x$ by $e$, but I'm getting the wrong result:
Does anybody know how to get the correct expression of that generic derivative evaluated at $e$?