fix(histogram): ensure that the bin width calculation matches numpy

This commit ensures the bin width calculation for the `histogram` API
matches numpy's implementation. There's still some work to do to ensure
the final calculation matches (the buckets aren't quite matching yet),
but this gets us closer to the desired outcome.

ibis/backends/dask/execution/generic.py

@@ -34,6 +34,7 @@
     date_types,
     integer_types,
     numeric_types,
+    scalar_types,
     simple_types,
     timestamp_types,
 )
@@ -361,6 +362,9 @@ def execute_not_scalar_or_series(op, data, **kwargs):
 @execute_node.register(ops.Binary, dd.Series, dd.Series)
 @execute_node.register(ops.Binary, dd.Series, dd.core.Scalar)
 @execute_node.register(ops.Binary, dd.core.Scalar, dd.Series)
+@execute_node.register(ops.Binary, dd.core.Scalar, scalar_types)
+@execute_node.register(ops.Binary, scalar_types, dd.core.Scalar)
+@execute_node.register(ops.Binary, dd.core.Scalar, dd.core.Scalar)
 @execute_node.register(
     (ops.NumericBinary, ops.LogicalBinary, ops.Comparison),
     numeric_types,

ibis/backends/tests/test_numeric.py

@@ -1371,8 +1371,10 @@ def test_clip(backend, alltypes, df, ibis_func, pandas_func):
 )
 def test_histogram(con, alltypes):
     n = 10
-    results = con.execute(alltypes.int_col.histogram(n).name("tmp"))
-    assert len(results.value_counts()) == n
+    hist = con.execute(alltypes.int_col.histogram(n).name("hist"))
+    vc = hist.value_counts().sort_index()
+    vc_np, _bin_edges = np.histogram(alltypes.int_col.execute(), bins=n)
+    assert vc.tolist() == vc_np.tolist()
 
 
 @pytest.mark.parametrize("const", ["pi", "e"])

ibis/expr/types/numeric.py

@@ -1032,17 +1032,13 @@ def histogram(
             )
 
         if binwidth is None or base is None:
-            import ibis
-
             if nbins is None:
                 raise ValueError("`nbins` is required if `binwidth` is not provided")
 
-            empty_window = ibis.window()
-
             if base is None:
-                base = self.min().over(empty_window) - eps
+                base = self.min() - eps
 
-            binwidth = (self.max().over(empty_window) - base) / (nbins - 1)
+            binwidth = (self.max() - base) / nbins
 
         return ((self - base) / binwidth).floor()