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def diff(a, n=1, axis=-1):
    """
    Calculate the n-th order discrete difference along given axis.
 
    The first order difference is given by ``out[n] = a[n+1] - a[n]`` along
    the given axis, higher order differences are calculated by using `diff`
    recursively.
 
    Parameters
    ----------
    a : array_like
        Input array
    n : int, optional
        The number of times values are differenced.
    axis : int, optional
        The axis along which the difference is taken, default is the last axis.
 
    Returns
    -------
    out : ndarray
        The `n` order differences. The shape of the output is the same as `a`
        except along `axis` where the dimension is smaller by `n`.
 
    See Also
    --------
    gradient, ediff1d
 
    Examples
    --------
    >>> x = np.array([1, 2, 4, 7, 0])
    >>> np.diff(x)
    array([ 1,  2,  3, -7])
    >>> np.diff(x, n=2)
    array([  1,   1, -10])
 
    >>> x = np.array([[1, 3, 6, 10], [0, 5, 6, 8]])
    >>> np.diff(x)
    array([[2, 3, 4],
           [5, 1, 2]])
    >>> np.diff(x, axis=0)
    array([[-1,  2,  0, -2]])
 
    """
    if n == 0:
        return a
    if n < 0:
        raise ValueError(
                "order must be non-negative but got " + repr(n))
    a = asanyarray(a)
    nd = len(a.shape)
    slice1 = [slice(None)]*nd
    slice2 = [slice(None)]*nd
    slice1[axis] = slice(1, None)
    slice2[axis] = slice(None, -1)
    slice1 = tuple(slice1)
    slice2 = tuple(slice2)
    if n > 1:
        return diff(a[slice1]-a[slice2], n-1, axis=axis)
    else:
        return a[slice1]-a[slice2]