checkpoint

distribution/lib/Standard/Table/0.2.32-SNAPSHOT/src/Internal/Table_Helpers.enso

@@ -47,6 +47,7 @@ select_columns internal_columns selector reorder on_problems warnings =
             result = Matching.match_criteria internal_columns names reorder=reorder name_mapper=(_.name) matching_strategy=matching_strategy on_problems=on_problems warnings=warnings
             Warnings.map_warnings_and_errors promote_no_matches_to_missing_columns result
         By_Index indices ->
+            # TODO partition indices into valid and invalid ones, so that we can report a warning or error
             result = case reorder of
                 True ->
                     here.select_indices_reordering internal_columns indices
@@ -75,4 +76,11 @@ select_indices_reordering vector indices =
    The elements are returned in the same order as they appeared in the original vector.
 select_indices_preserving_order vector indices =
     indices_to_keep = Map.from_vector (indices.map i-> [i, True])
-    vector.map_with_index
+    vector.filter_with_index ix-> elem->
+        indices_to_keep.get_or_else ix False
+
+## PRIVATE
+   Checks if the given index is in the valid range for the provided vector.
+is_index_valid vector ix =
+    actual_ix = if ix < 0 then vector.length+ix else ix
+    ix>=0 && ix<vector.length