Add back diff (was missing)

1 files changed, 19 insertions, 0 deletions

diff --git a/mdpoly/expressions.py b/mdpoly/expressions.py
index 6d855a3..9fa07f2 100644
--- a/mdpoly/expressions.py
+++ b/mdpoly/expressions.py
@@ -296,3 +296,22 @@ class WithOps:
 
     def __rtruediv__(self, other: Any) -> Self:
         raise NotImplementedError
+
+    # --- More operations ---
+
+    @wrap_result
+    def diff(self, with_respect_to: WithOps) -> Expr:
+        with self as expr, with_respect_to as wrt:
+            if not isinstance(wrt, Var):
+                raise AlgebraicError(
+                        f"Cannot differentate {str(self.expr)} with respect to "
+                        f"{str(wrt)}. We can only differentiate with respect to "
+                        f"variables (type {Var}).")
+
+            # TODO: implement vector derivatives
+            return PolyPartialDiff(expr, wrt=wrt)
+
+
+    @wrap_result
+    def integrate(self, with_respect_to: WithOps) -> Expr:
+        raise NotImplementedError