On 5/24/07, Andrej Vodopivec <andrej.vodopivec at gmail.com> wrote:
>
> Anyway, zeta(x) is an evaluated function and psi[0](x) is a
> simplifying function if I remember correctly. What is a user-visible
> difference between them?
>
There is no resimplification after subst with an evaluating function:
subst(2,x,zeta(x)) => zeta(2) (really 'zeta(2) )
ev( 'zeta(2) , nouns) => %pi^2/6 -- invoking evaluator
zeta(2) => %pi^2/6
subst(2,x,psi[0](x)) => 1-%gamma
psi[0](2) => 1-%gamma
All mathematical functions like zeta should become simplifying functions.
-s