Function: nffactorback
Section: number_fields
C-Name: nffactorback
Prototype: GGDG
Help: nffactorback(nf,f,{e}): given a factorization f, returns
the factored object back as an nf element.
Doc: gives back the \var{nf} element corresponding to a factorization.
The integer $1$ corresponds to the empty factorization.
If $e$ is present, $e$ and $f$ must be vectors of the same length ($e$ being
integral), and the corresponding factorization is the product of the
$f[i]^{e[i]}$.
If not, and $f$ is vector, it is understood as in the preceding case with $e$
a vector of 1s: we return the product of the $f[i]$. Finally, $f$ can be a
regular factorization matrix.
\bprog
? nf = nfinit(y^2+1);
? nffactorback(nf, [3, y+1, [1,2]~], [1, 2, 3])
%2 = [12, -66]~
? 3 * (I+1)^2 * (1+2*I)^3
%3 = 12 - 66*I
@eprog