Green

distribution/lib/Standard/Table/0.0.0-dev/src/Column.enso

@@ -2633,18 +2633,19 @@ type Column
     @default (self-> Widget_Helpers.make_fill_default_value_selector2 value_types=self.value_type)
     offset : Integer -> Column | Previous_Value | Any  -> Column
     offset self n=-1:Integer default:OffFill=..Nothing -> Column =
-        as_vector = self.to_vector
-        fill_vector = case default of
-            OffFill.Nothing -> Vector.fill n.abs Nothing
-            OffFill.Closest_Value -> if n<0 then Vector.fill n.abs (as_vector.at 0) else Vector.fill n.abs (as_vector.at (self.length-1))
-            OffFill.Wrap_Around -> if n<0 then as_vector.take (..Last n.abs) else as_vector.take (..First n)
-            OffFill.Constant constant -> Vector.fill n.abs constant
-
-        offset_vector = if n > 0 then as_vector + fill_vector else
-            fill_vector + as_vector
-        resized_vector = if n > 0 then offset_vector.take (..Last self.length) else
-            offset_vector.take (..First self.length)
-        Column.from_vector self.name resized_vector
+        if self.length == 0 then self else
+          as_vector = self.to_vector
+          fill_vector = case default of
+              OffFill.Nothing -> Vector.fill n.abs Nothing
+              OffFill.Closest_Value -> if n<0 then Vector.fill n.abs (as_vector.at 0) else Vector.fill n.abs (as_vector.at (self.length-1))
+              OffFill.Wrap_Around -> if n<0 then as_vector.take (..Last n.abs) else as_vector.take (..First n)
+              OffFill.Constant constant -> Vector.fill n.abs constant
+
+          offset_vector = if n > 0 then as_vector + fill_vector else
+              fill_vector + as_vector
+          resized_vector = if n > 0 then offset_vector.take (..Last self.length) else
+              offset_vector.take (..First self.length)
+          Column.from_vector self.name resized_vector
 
     ## PRIVATE
     pretty : Text

test/Table_Tests/src/Common_Table_Operations/Offset_Spec.enso

@@ -4,6 +4,9 @@ from Standard.Test import all
 from Standard.Database.Errors import Unsupported_Database_Operation
 import Standard.Database.Feature.Feature
 
+from project.Common_Table_Operations.Util import run_default_backend
+import project.Common_Table_Operations.Util
+
 main filter=Nothing = run_default_backend add_specs filter
 
 add_specs suite_builder setup =
@@ -18,6 +21,57 @@ add_specs suite_builder setup =
                 c2 = c.offset
                 c2.should_fail_with (Unsupported_Database_Operation.Error "offset")
 
-add_filter_specs suite_builder setup =
+add_offset_specs suite_builder setup =
     prefix = setup.prefix
-    table_builder = setup.light_table_builder
+    build_sorted_table = Util.build_sorted_table setup
+    t = build_sorted_table [["A", [1, 2, 3]], ["B", [Nothing, Nothing, Nothing]]]
+    c = t.at 0 
+    c_nothings = t.at 1
+    c_zero_rows = t.take 0 . at 0
+    suite_builder.group prefix+"Column.Offset with default fill strategy" group_builder->
+        group_builder.specify "Works with default values" <|
+            r = c.offset
+            r.to_vector . should_equal [Nothing, 1, 2]
+        group_builder.specify "Negative n shifts the values down" <|
+            r = c.offset -1
+            r.to_vector . should_equal [Nothing, 1, 2]
+        group_builder.specify "Positive n shifts the values up" <|
+            r = c.offset 1
+            r.to_vector . should_equal [2, 3, Nothing]
+        group_builder.specify "Zero n is a no-op" <|
+            r = c.offset 0
+            r.to_vector . should_equal [1, 2, 3]
+        group_builder.specify "Large negative n values work" <|
+            r = c.offset -1024
+            r.to_vector . should_equal [Nothing, Nothing, Nothing]
+        group_builder.specify "Large positive n values work" <|
+            r = c.offset 1024
+            r.to_vector . should_equal [Nothing, Nothing, Nothing]
+        group_builder.specify "Works with zero rows" <|
+            r = c_zero_rows.offset
+            r.to_vector . should_equal []
+    suite_builder.group prefix+"Column.Offset with closest value fill strategy" group_builder->
+        group_builder.specify "Negative n shifts the values down" <|
+            r = c.offset -1 ..Closest_Value
+            r.to_vector . should_equal [1, 1, 2]
+        group_builder.specify "Positive n shifts the values up" <|
+            r = c.offset 1 ..Closest_Value
+            r.to_vector . should_equal [2, 3, 3]
+        group_builder.specify "Zero n is a no-op" <|
+            r = c.offset 0 ..Closest_Value
+            r.to_vector . should_equal [1, 2, 3]
+        group_builder.specify "Large negative n values work" <|
+            r = c.offset -1024 ..Closest_Value
+            r.to_vector . should_equal [1, 1, 1]
+        group_builder.specify "Large positive n values work" <|
+            r = c.offset 1024 ..Closest_Value
+            r.to_vector . should_equal [3, 3, 3]
+        group_builder.specify "Works with zero rows" <|
+            r = c_zero_rows.offset -1 ..Closest_Value
+            r.to_vector . should_equal []
+        group_builder.specify "Works with negative n and column of nothings" <|
+            r = c_nothings.offset -1 ..Closest_Value
+            r.to_vector . should_equal [Nothing, Nothing, Nothing]
+        group_builder.specify "Works with positive n and column of nothings" <|
+            r = c_nothings.offset 1 ..Closest_Value
+            r.to_vector . should_equal [Nothing, Nothing, Nothing]