'Evaluates ``f`` at the given point ``a`` in ``x_j``.'

def eval(f, a, j=0):

    if (not isinstance(j, int)):
        raise TypeError(('``int``    expected,    got    %s' % type(j)))
    return f.per(dmp_eval_in(f.rep, f.dom.convert(a), j, f.lev, f.dom), kill=True)
