- Usage:
`PolyExt M, PolyExt I; RatExt(i,M), RatExt(i,I)`

- Outputs:
- a hash table or a module, the Ext
^{i}group(s) between holonomic*M*and the polynomial ring

- a hash table or a module, the Ext

The `Ext` groups between a D-module *M* and the polynomial ring are the derived functors of `Hom`, and are finite-dimensional vector spaces over the ground field when *M* is holonomic.

The algorithm used appears in the paper 'Polynomial and rational solutions of holonomic systems' by Oaku-Takayama-Tsai (2000). The method is to combine isomorphisms of Bjork and Kashiwara with the restriction algorithm.

i1 : W = QQ[x, D, WeylAlgebra=>{x=>D}] o1 = W o1 : PolynomialRing |

i2 : M = W^1/ideal(x^2*D^2) o2 = cokernel | x2D2 | 1 o2 : W-module, quotient of W |

i3 : PolyExt(M) 2 o3 = HashTable{0 => QQ } 2 1 => QQ o3 : HashTable |

Does not yet compute explicit representations of Ext groups such as Yoneda representation.

- PolySols -- polynomial solutions of a holonomic system
- RatExt -- Ext(holonomic D-module, polynomial ring localized at the sigular locus)
- DExt -- Ext groups between holonomic modules
- Dintegration -- integration modules of a D-module

- PolyExt(Ideal)
- PolyExt(Module)
- PolyExt(ZZ,Ideal)
- PolyExt(ZZ,Module)