Fix projections and fix test for projection, add sum behavior (#141)

Author: henryiii

boost_histogram/_hist.py

@@ -110,7 +110,7 @@ def _compute_getitem(self, index):
     except RuntimeError:
         pass
 
-    projections = []
+    integrations = set()
     slices = []
 
     # Compute needed slices and projections
@@ -125,7 +125,7 @@ def _compute_getitem(self, index):
             if ind.step is not None:
                 if hasattr(ind.step, "projection"):
                     if ind.step.projection:
-                        projections.append(i)
+                        integrations.add(i)
                         if ind.start is not None or ind.stop is not None:
                             raise IndexError(
                                 "Currently cut projections are not supported"
@@ -150,7 +150,11 @@ def _compute_getitem(self, index):
             slices.append(_core.algorithm.slice_and_rebin(i, begin, end, merge))
 
     reduced = self.reduce(*slices)
-    return reduced.project(*projections) if projections else reduced
+    if not integrations:
+        return reduced
+    else:
+        projections = [i for i in range(self.rank) if i not in integrations]
+        return reduced.project(*projections) if projections else self.sum(flow=True)
 
 
 def _compute_setitem(self, index, value):

tests/test_indexing.py

@@ -92,12 +92,18 @@ def test_ellipsis():
 
 
 def test_basic_projection():
-    h2 = bh.histogram(bh.axis.regular(10, 0, 1), bh.axis.regular(10, 0, 1))
-    h1 = bh.histogram(bh.axis.regular(10, 0, 1))
+    h2 = bh.histogram(
+        bh.axis.regular(10, 0, 10),
+        bh.axis.regular(10, 0, 10),
+        bh.axis.regular(10, 0, 10),
+    )
+    h1 = bh.histogram(bh.axis.regular(10, 0, 10))
 
-    contents = [[2, 2, 2, 3, 4, 5, 6], [1, 2, 2, 3, 2, 1, 2]]
+    contents = [[2, 2, 2, 3, 4, 5, 6], [1, 2, 2, 3, 2, 1, 2], [-12, 33, 4, 9, 2, 4, 9]]
 
     h1.fill(contents[0])
     h2.fill(*contents)
 
-    assert h1 == h2[:, :: bh.project]
+    assert h1 == h2[:, :: bh.project, :: bh.project]
+    assert h1 == h2[..., :: bh.project, :: bh.project]
+    assert h2.sum(flow=True) == h2[:: bh.project, :: bh.project, :: bh.project]