Constructs ternary implication coding (0=not there, 2=U, 1=V)
    t is B column position
    i = |M|-1 to 0

def B012(t,i):
    """
    Constructs ternary implication coding (0=not there, 2=U, 1=V)
    t is B column position
    i = |M|-1 to 0
    """
    if not i:
        return "1"
    nA = Awidth(i)
    nB = Bwidth(i)
    nBB = nB + nA
    if t < nB:
        return "0"+B012(t,i-1)
    elif t < nBB:
        return "1"+A012(t-nB,i-1)
    else:
        return "2"+B012(t-nBB,i-1)