# using pade approx

Hi 1) From the only example I found s = PowerSeriesRing(QQ,'s').gen() a=exp(s);a.pade(4, 0) type(a)

it seems this works for type 'sage.rings.power_series_poly.PowerSeries_poly'

But I have a type 'sage.symbolic.expression.Expression' b, and was unable to convert b to the type required to apply pade

2) There's an alternative rational.reconstruct , but that seems to be geared to computations modulo (n) 3) In conclusion, it seems at current stage the simplest is to write one's own Pade? Thanks, Florin

`b`

from (1), so that potential helpers have a clear idea what kind of expressions are involved, and give the solution working in that particular case in any case.`rational_reconstruction`

, indeed. But i do not see it as an alternative, it is designed only for the special use described in its doc string, offered e.g. by typing`rational_reconstruction?`

in the sage interpreter.`pade`

method inside the class where it is genuinely defined. So just start with a`b`

which is some function in`s`

- say, convert is somehow to a power series, get the result, and possibly come back. But why do we need such a complication, why is the input`b`

not directly in the`PowerSeriesRing`

of`QQ`

?!