Fix rebinning logic

src/boost_histogram/_internal/hist.py

@@ -851,9 +851,9 @@ def __getitem__(self: H, index: IndexingExpr) -> H | float | Accumulator:
             # This ensures that callable start/stop are handled
             start, stop = self.axes[i]._process_loc(ind.start, ind.stop)
 
+            groups = []
             if ind != slice(None):
                 merge = 1
-                groups = []
                 if ind.step is not None:
                     if getattr(ind.step, "factor", None) is not None:
                         merge = ind.step.factor
@@ -891,10 +891,11 @@ def __getitem__(self: H, index: IndexingExpr) -> H | float | Accumulator:
                     axes = [reduced.axis(x) for x in range(reduced.rank())]
                     reduced_view = reduced.view(flow=True)
                     new_axes_indices = [axes[i].edges[0]]
+
                     j: int = 0
                     for group in groups:
                         new_axes_indices += [axes[i].edges[j + 1 : j + group + 1][-1]]
-                        j = group
+                        j += group
 
                     variable_axis = Variable(
                         new_axes_indices, metadata=axes[i].metadata
@@ -906,16 +907,16 @@ def __getitem__(self: H, index: IndexingExpr) -> H | float | Accumulator:
 
                     logger.debug("Axes: %s", axes)
 
-                    # redistribute the bin contents here
-
                     new_reduced = reduced.__class__(axes)
-                    new_reduced.view(flow=True)[...] = reduced_view
+                    new_reduced.fill(
+                        np.add.reduceat(reduced.to_numpy()[0], new_axes_indices, axis=i)
+                    )
                     reduced = new_reduced
 
         # Will be updated below
         if slices or pick_set or pick_each or integrations:
             reduced = self._hist
-        else:
+        elif len(groups) == 0:
             logger.debug("Reduce actions are all empty, just making a copy")
             reduced = copy.copy(self._hist)
 

src/boost_histogram/tag.py

@@ -130,7 +130,7 @@ def __init__(
     def __repr__(self) -> str:
         repr_str = f"{self.__class__.__name__}"
         args: dict[str, int | Sequence[int] | None] = {
-            "value": self.factor,
+            "factor": self.factor,
             "groups": self.groups,
         }
         for k, v in args.items():

tests/test_histogram_indexing.py

@@ -240,7 +240,7 @@ def test_repr():
     assert repr(bh.overflow + 1) == "overflow + 1"
     assert repr(bh.overflow - 1) == "overflow - 1"
 
-    assert repr(bh.rebin(2)) == "Rebinner(value=2)"
+    assert repr(bh.rebin(2)) == "Rebinner(factor=2)"
 
 
 # Was broken in 0.6.1