Implement grouping. First steps towards #6292

distribution/lib/Standard/Table/0.0.0-dev/src/Internal/Add_Row_Number.enso

@@ -5,6 +5,7 @@ import project.Data.Column_Selector.Column_Selector
 import project.Data.Sort_Column.Sort_Column
 import project.Data.Set_Mode.Set_Mode
 import project.Data.Table.Table
+import project.Internal.Multi_Value_Key.Multi_Value_Key
 import project.Internal.Problem_Builder.Problem_Builder
 import project.Internal.Table_Helpers
 import project.Internal.Unique_Name_Strategy.Unique_Name_Strategy
@@ -23,7 +24,7 @@ add_row_number table name="Row" from=1 step=1 group_by=[] order_by=[] on_problem
             True ->
                 case grouping_columns.is_empty of
                     True -> make_range_column name from step table.row_count
-                    False -> Error.throw "TODO: not implemented yet"
+                    False -> make_grouped_enumeration name grouping_columns from step
             False -> Error.throw "TODO: not implemented yet"
 
         column_names = table.column_names
@@ -38,10 +39,27 @@ add_row_number table name="Row" from=1 step=1 group_by=[] order_by=[] on_problem
                 Table.new new_columns
         renamed_table.set new_column name set_mode=Set_Mode.Add
 
+## PRIVATE
+nth_index start step n =
+    start + n*step
+
 ## PRIVATE
 make_range_column name start step length =
     builder = make_long_builder length
     0.up_to length . each ix->
-        builder.appendLong (start + ix*step)
+        builder.appendLong (nth_index start step ix)
     storage = builder.seal
     Column.from_storage name storage
+
+## PRIVATE
+make_grouped_enumeration name grouping_columns start step =
+    n = grouping_columns.at 0 . length
+    column_builder = make_long_builder n
+    0.up_to n . fold Map.empty grouping_counters-> ix->
+        key = Multi_Value_Key.from_row grouping_columns ix
+        enum_index = grouping_counters.get key 0
+        column_builder.appendLong (nth_index start step enum_index)
+        new_counters = grouping_counters.insert key (enum_index + 1)
+        new_counters
+    storage = column_builder.seal
+    Column.from_storage name storage

distribution/lib/Standard/Table/0.0.0-dev/src/Internal/Multi_Value_Key.enso

@@ -0,0 +1,41 @@
+from Standard.Base import all
+import Standard.Base.Data.Array_Proxy.Array_Proxy
+import Standard.Base.Errors.Illegal_State.Illegal_State
+
+## PRIVATE
+   An Enso implementation mirroring `OrderedMultiValueKey` and
+   `UnorderedMultiValueKey` from the Java helpers.
+
+   The ordered part is implemented by delegating to comparators of its elements.
+
+   The unordered part is implemented by delegating to the hahses of elements.
+type Multi_Value_Key
+    ## PRIVATE
+    Key values:Vector
+
+    ## PRIVATE
+    from_row columns row_index =
+        arr = Array_Proxy.new columns.length column_ix->
+            columns . at column_ix . at row_index
+        values = Vector.from_polyglot_array arr
+        Multi_Value_Key.Key values
+
+## PRIVATE
+type Multi_Value_Key_Comparator
+    ## PRIVATE
+    compare x y =
+        n = x.values.length
+        if n != y.values.length then Panic.throw (Illegal_State.Error "Multi_Value_Key used with different number of values: " + x.to_text + " vs " + y.to_text) else
+            go ix =
+                if ix >= n then Ordering.Equal else
+                    vx = x.values . at ix
+                    vy = y.values . at ix
+                    cmp = (Comparable.from vx).compare vx vy
+                    if cmp != Ordering.Equal then cmp else
+                        @Tail_Call go (ix + 1)
+            go 0
+
+    ## PRIVATE
+    hash x = (Comparable.from x.values).hash x.values
+
+Comparable.from (_:Multi_Value_Key) = Multi_Value_Key_Comparator