def make_matrix(rows, cols, fill=0.0):
    """Returns a matrix (list of list of floats) using a default
    value.

    :param rows: Number of rows
    :type rows: int
    :param cols: Number of columns
    :type cols: int
    :param fill: Default value for each element in the matrix
    :type fill: float
    """
    m = []
    for i in range(rows):
        m.append([fill] * cols)
    return m