def dirac_delta_function(x, steps=[(1, 1)]):
    """
    Returns a Dirac delta function such that

    f(x) = y_0 if x = x_0,
           y_1 if x = x_1,
           ...
           else 0

    Parameters
    ============
    x: the input value.
    steps: a list of deltas.
    """
    for x_n, y_n in steps:
        if x == x_n:
            return y_n
    else:
        return 0