Add helper method WithOps.to_sparse to give sparse representation

1 files changed, 14 insertions, 2 deletions

diff --git a/mdpoly/expressions.py b/mdpoly/expressions.py
index 159769e..8836c52 100644
--- a/mdpoly/expressions.py
+++ b/mdpoly/expressions.py
@@ -6,9 +6,10 @@ from dataclasses import dataclass
 from functools import wraps
 from typing import Type, TypeVar, Iterable, Callable, Sequence, Any, Self, cast
 
-from .abc import Expr, Var, Const, Param
+from .abc import Expr, Var, Const, Param, Repr
 from .index import Shape, MatrixIndex, PolyIndex, PolyVarIndex, Number
 from .errors import MissingParameters, AlgebraicError
+from .representations import SparseRepr
 
 from .operations.add import MatAdd, MatSub
 from .operations.mul import MatElemMul
@@ -326,7 +327,18 @@ class WithOps:
             # TODO: implement vector derivatives
             return PolyPartialDiff(expr, wrt=wrt)
 
-
     @wrap_result
     def integrate(self, with_respect_to: WithOps) -> Expr:
         raise NotImplementedError
+
+    # -- Make representations ---
+
+    def to_sparse(self, state: State) -> tuple[SparseRepr, State]:
+        """ Make a sparse representation.
+
+        See :py:class:`mdpoly.representations.SparseRepr`
+        """
+        return self.unwrap().to_repr(SparseRepr, state)
+
+    def to_dense(self, state: State) -> tuple[Repr, State]:
+        raise NotImplementedError