expr: fix reverse for << and >>

sx/core/expr.py

@@ -89,8 +89,8 @@ reverse = {
     operator.pow: lambda x, y: math.log(x) / math.log(y),
 
     operator.inv:    operator.inv,
-    operator.lshift: operator.rshift,
-    operator.rshift: operator.lshift,
+    operator.lshift: (operator.rshift, lambda x, y: int(math.log(x / y) / math.log(2))),
+    operator.rshift: (operator.lshift, lambda x, y: int(math.log(y / x) / math.log(2))),
 }
 
 T = TypeVar('T')
@@ -121,9 +121,10 @@ class Expr(G[T]):
         locals()['__' + x.strip('_') + '__'] = functools.partialmethod(lambda self, x: UnaryExpr(getattr(operator, x), self), x)
     for x in (
         'add', 'and_', 'floordiv', 'lshift', 'mod', 'mul', 'matmul', 'or_', 'pow', 'rshift', 'sub', 'truediv', 'xor',
-        'concat', 'contains', 'delitem', 'getitem', 'delitem', 'getitem', 'setitem',
+        'concat', 'contains',
     ):
-        locals()['__' + x.strip('_') + '__'] = functools.partialmethod(lambda self, x, other: BinExpr(getattr(operator, x), self, other), x)
+        locals()[ '__' + x.strip('_') + '__'] = functools.partialmethod(lambda self, x, other: BinExpr(getattr(operator, x), self, other), x)
+        locals()['__r' + x.strip('_') + '__'] = functools.partialmethod(lambda self, x, other: BinExpr(getattr(operator, x), other, self), x)
     del x
 
 class AttrExpr(G[T], Expr[T]):
@@ -263,14 +264,19 @@ class BinExpr(G[T], Expr[T]):
         if not isinstance(self.__left, Expr):
             operand = self.__left
             target = self.__right
+            i = 0
         elif not isinstance(self.__right, Expr):
             operand = self.__right
             target = self.__left
+            i = 1
         else:
             raise NotImplementedError(f'{self.__class__.__name__} has two expression operands and is not invertible')
         if self.__op not in reverse:
             raise NotImplementedError(f'{self.__class__.__name__} {symbols[self.__op]!r} is not invertible')
-        put(target, reverse[self.__op](value, operand))
+        rev = reverse[self.__op]
+        if isinstance(rev, tuple):
+            rev = rev[i]
+        put(target, rev(value, operand))
 
     def __str__(self) -> str:
         return f'({self.__left} {symbols[self.__op]} {self.__right})'