Function: idealchinese
Section: number_fields
C-Name: idealchinese
Prototype: GGG
Help: idealchinese(nf,x,y): x being a prime ideal factorization and y a
 vector of elements, gives an element b such that v_p(b-y_p)>=v_p(x) for all
 prime ideals p dividing x, and v_p(b)>=0 for all other p.
Doc: $x$ being a prime ideal factorization
 (i.e.~a 2 by 2 matrix whose first column contains prime ideals, and the second
 column integral exponents), $y$ a vector of elements in $\var{nf}$ indexed by
 the ideals in $x$, computes an element $b$ such that

 $v_{\goth{p}}(b - y_{\goth{p}}) \geq v_{\goth{p}}(x)$ for all prime ideals
 in $x$ and $v_{\goth{p}}(b)\geq 0$ for all other $\goth{p}$.
