Function: nfbasistoalg
Section: number_fields
C-Name: basistoalg
Prototype: GG
Help: nfbasistoalg(nf,x): transforms the column vector x on the integral
 basis into an algebraic number.
Doc: Given an algebraic number $x$ in the number field \var{nf}, transforms it
 into \typ{POLMOD} form.
 \bprog
 ? nf = nfinit(y^2 + 4);
 ? nf.zk
 %2 = [1, 1/2*y]
 ? nfbasistoalg(nf, [1,1]~)
 %3 = Mod(1/2*y + 1, y^2 + 4)
 ? nfbasistoalg(nf, y)
 %4 = Mod(y, y^2 + 4)
 ? nfbasistoalg(nf, Mod(y, y^2+4))
 %5 = Mod(y, y^2 + 4)
 @eprog
 This is the inverse function of \kbd{nfalgtobasis}.
