Method tryInvert

factory/int_poly.cc:263–283

}

InternalCF*
InternalPoly::tryInvert ( const CanonicalForm& M, bool& fail)
{
  if ( inExtension() && !getReduce ( var ) )
  {
    CanonicalForm b, inverse;
    CanonicalForm F ( this ->copyObject() );
    Variable a = M.mvar();
    Variable x = Variable(1);
    F= mod (F, M); //reduce mod M
    CanonicalForm g= extgcd (replacevar( F, a, x ), replacevar( M, a, x ), inverse, b );
    if(!g.isOne())
      fail = true;
    else
      inverse = replacevar( inverse, x, a ); // change back to alg var
    CanonicalForm test= mod (inverse*F, M);
    return inverse.getval();
  }
  else
    return CFFactory::basic( 0 );
}

InternalCF*
InternalPoly::addsame( InternalCF* aCoeff )