Function: polisclass
Section: polynomials
C-Name: polisclass
Prototype: lG
Help: polisclass(P): P being a monic irreducible polynomial with integer
 coefficients, return 0 if P is not a class polynomial for the j-invariant,
 otherwise return the discriminant D<0 such that P=polclass(D).
Doc: $P$ being a monic irreducible polynomial with integer coefficients,
 return $0$ if $P$ is not a class polynomial for the $j$-invariant,
 otherwise return the discriminant $D<0$ such that \kbd{P=polclass(D)}.
 \bprog
 ? polisclass(polclass(-47))
 %1 = -47
 ? polisclass(x^5+x+1)
 %2 = 0
 ? apply(polisclass,factor(poldisc(polmodular(5)))[,1])
 %3 = [-16,-4,-3,-11,-19,-64,-36,-24,-51,-91,-99,-96,-84]~
 @eprog
