1 files changed, 39 insertions, 0 deletions
diff --git a/mdpoly/sos/representations.py b/mdpoly/sos/representations.py
new file mode 100644
index 0000000..9261b82
--- /dev/null
+++ b/mdpoly/sos/representations.py
@@ -0,0 +1,39 @@
+from __future__ import annotations
+from typing import TYPE_CHECKING
+
+from typing import Iterable
+import cvxopt
+
+from ..abc import Repr
+
+if TYPE_CHECKING:
+    from ..index import MatrixIndex, PolyIndex, Number, Shape
+
+
+class CVXOptSparseMatrixRepr(Repr):
+    data: cvxopt.spmatrix
+
+    def __init__(self, shape: Shape):
+        self.data = cvxopt.spmatrix(0, size=shape)
+
+    def at(self, entry: MatrixIndex, term: PolyIndex) -> Number:
+        """ Access polynomial coefficient. """
+        return self.data[entry.row, entry.col]
+
+    def set(self, entry: MatrixIndex, term: PolyIndex, value: Number) -> None:
+        """ Set value of polynomial coefficient. """
+        raise NotImplementedError
+
+    def set_zero(self, entry: MatrixIndex, term: PolyIndex) -> None:
+        """ Set a coefficient to zero (delete it). """
+        raise NotImplementedError
+
+    def entries(self) -> Iterable[MatrixIndex]:
+        """ Return indices to non-zero entries of the matrix. """
+        raise NotImplementedError
+
+    def terms(self, entry: MatrixIndex) -> Iterable[PolyIndex]:
+        """ Return indices to non-zero terms in the polynomial at the given
+        matrix entry. """
+        raise NotImplementedError
+