A sage implementation for DD-finite functions

We present here the Sage package dd_functions which provides many features to compute with DD-finite functions, a natural extension of the class of holonomic or D-finite functions. The package, focused on a functional approach, allows the user to compute closure properties, extract coefficient sequences and compute the composition (as formal power series) of functions treated in this package. All these operations reduce the problem to linear algebra computations where classical division-free algorithms are used.