    Arg0

    (   Arg0    + 0) * 1 + 0
    [(1 - Arg0) + 0] * 1 + 0

    invert = 0
    a_mode = TEXENV_SETUP_MODE(Arg0, 0)
    b_mode = 0
    c_mode = 0
    c_invt = 1
    d_mode = 0
    d_invt = 0

A_OK:
    (Arg0 + 0) * 1 + 0 = Arg0
A_INVERT:
    (1_Arg0 + 0) * 1 + 0 = 1_Arg0
