differentiation - Maxima: evaluate a function f(x) embedding diff() nouns -

i generate taylor series following these instructions :

f(x) := ''(ratdisrep(taylor(qexct('x),'x,0,5))); 

qexct function not defined : want perform computation qexct smooth function.

knowing this, how set variable x value (e.g. 1) ?

if :

f(1); 

then maxima returns me following error :

diff: variable must not number; found: 1 

and if :

f(d); 

then considers d variable , substitutes occurrences of variable x variable d. in particular, differentiates using d/dd instead of d/dx. however, substitute variable x number 1 in x^n terms , keep derivatives are…

how do ?

the variable in diff expression not recognized everywhere in maxim dummy (formal) variable, when try evaluate f(1), maxima substitutes 1 diff expression , causes error. think that's bug; i'll make bug report it.

as work around, can use add-on package pdiff (positional derivatives) included maxima. notation little different dy/dx notation used default in maxima.

(%i1) load (pdiff) $ (%i2) f(x) := ''(ratdisrep(taylor(qexct('x),'x,0,2)));                                     2                      qexct     (0) x                           ""(2) (%o2)        f(x) := ---------------- + qexct     (0) x + qexct(0)                             2                ""(1) (%i3) f(h);                                 2                    qexct   (0) h                         (2) (%o3)              -------------- + qexct   (0) h + qexct(0)                          2               (1) (%i4) ev (%, qexct=sin); (%o4)                                  h (%i5) ev (%o3, h=1);                      qexct   (0)                           (2) (%o5)                ----------- + qexct   (0) + qexct(0)                           2             (1) 

i think spurious "" in display of f(x) := ... minor display bugs; think can ignore them.

there documentation pdiff in share/pdiff/pdiff-doc.pdf in maxima installation.