Improve algebra.unary_operator decorator

1 files changed, 29 insertions, 13 deletions

diff --git a/mdpoly/algebra.py b/mdpoly/algebra.py
index d44a528..78e4965 100644
--- a/mdpoly/algebra.py
+++ b/mdpoly/algebra.py
@@ -16,19 +16,6 @@ from abc import abstractmethod
 import operator
 
 
-def unary_operator(cls: Expr) -> Expr:
-    """ Class decorator to modify constructor of unary operators. """
-    __init_cls__ = cls.__init__
-    @wraps(cls.__init__)
-    def __init_unary__(self, left, *args, **kwargs):
-        __init_cls__(self, *args, **kwargs)
-        self.left, self.right = left, Nothing
-        self.inner = left
-
-    cls.__init__ = __init_unary__
-    return cls
-
-
 T = TypeVar("T")
 
 @runtime_checkable
@@ -140,6 +127,35 @@ def binary_operator(left_type: AlgebraicStructure, right_type: AlgebraicStructur
         return cls
     return decorator
 
+
+def unary_operator(inner_type: AlgebraicStructure):
+    """ Class decorator that adss constructor for unary operations of Expr
+
+    This is the special case of the binary operator, where only *left* is used
+    (because it is assumed that the operator acts from the left. The field for
+    *right* contains a placeholder :py:class:`mdpoly.leaves.Nothing`,
+    furthermore a new field *inner* is added as alias to *left*.
+
+    See also :py:fun:`mdpoly.algebra.binary_operator`.
+    """
+    def decorator(cls: Expr) -> Expr:
+        """ Class decorator to modify constructor of unary operators. """
+        init_cls = cls.__init__
+        @wraps(cls.__init__)
+        def new_init_cls(self, left, *args, **kwargs):
+            init_cls(self, *args, **kwargs)
+            self.left, self.right = left, Nothing
+
+        @property
+        def inner(self):
+            return self.left
+
+        cls.__init__ = new_init_cls
+        cls.inner = inner
+        return cls
+    return decorator
+
+
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