Add key functions to Table to make it act as [Column] (#3644)

Implements https://www.pivotaltracker.com/story/show/181370836

CHANGELOG.md

@@ -177,6 +177,8 @@
 - [Updated `Vector.take` and `Vector.drop` and removed their obsolete
   counterparts.][3629]
 - [Short-hand syntax for `order_by` added.][3643]
+- [Expanded `Table.at` to support index access and added `Table.column_count`
+  method.][3644]
 
 [debug-shortcuts]:
   https://github.com/enso-org/enso/blob/develop/app/gui/docs/product/shortcuts.md#debug
@@ -278,6 +280,7 @@
 [3617]: https://github.com/enso-org/enso/pull/3617
 [3629]: https://github.com/enso-org/enso/pull/3629
 [3643]: https://github.com/enso-org/enso/pull/3643
+[3644]: https://github.com/enso-org/enso/pull/3644
 [3648]: https://github.com/enso-org/enso/pull/3648
 
 #### Enso Compiler

distribution/lib/Standard/Database/0.0.0-dev/src/Data/Table.enso

@@ -16,7 +16,7 @@ import Standard.Table.Data.Aggregate_Column
 import Standard.Table.Internal.Aggregate_Column_Helper
 from Standard.Database.Data.Column import Column, Aggregate_Column_Builder
 from Standard.Database.Data.Internal.IR import Internal_Column
-from Standard.Table.Data.Table import No_Such_Column_Error
+from Standard.Table.Errors import No_Such_Column_Error
 from Standard.Table.Data.Column_Selector import Column_Selector, By_Index
 from Standard.Base.Data.Text.Text_Ordering import Text_Ordering
 from Standard.Table.Data.Data_Formatter import Data_Formatter
@@ -86,12 +86,18 @@ type Table
        Returns the column with the given name.
 
        Arguments:
-       - name: The name of the column to get.
-    at : Text -> Column ! No_Such_Column_Error
-    at self name =
-        candidates = self.internal_columns + self.context.meta_index
-        internal = candidates.find (p -> p.name == name)
-        self.make_column internal . map_error (_ -> No_Such_Column_Error name)
+       - selector: The name or index of the column to get.
+    at : Text | Integer -> Column ! No_Such_Column_Error | Index_Out_Of_Bounds_Error
+    at self selector=0 = case selector of
+        Integer -> self.make_column (self.internal_columns.at selector)
+        Text ->
+            candidates = self.internal_columns + self.context.meta_index
+            internal_column = candidates.find (p -> p.name == selector) . map_error (_ -> No_Such_Column_Error selector)
+            self.make_column internal_column
+
+    ## Returns the number of columns in the table.
+    column_count : Integer
+    column_count self = self.internal_columns.length
 
     ## Returns a new table with a chosen subset of columns, as specified by the
        `columns`, from the input table. Any unmatched input columns will be
@@ -423,7 +429,7 @@ type Table
        - index: The column to use as the index of the table.
     set_index : Text | Column | Vector Text -> Table
     set_index self index = Panic.recover Any <|
-        new_index = (Helpers.unify_vector_singleton index).map (self.at >> .as_internal)
+        new_index = (Helpers.unify_vector_singleton index).map ((self.at _) >> .as_internal)
         new_ctx = self.context.set_index new_index
         new_cols = self.internal_columns.filter col->
             turned_into_index = new_index.exists i-> i.name == col.name

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

@@ -19,7 +19,7 @@ from Standard.Table.Data.Column_Type_Selection import Column_Type_Selection, Aut
 from Standard.Table.Data.Data_Formatter import Data_Formatter
 from Standard.Base.Data.Text.Text_Ordering import Text_Ordering
 from Standard.Base.Error.Problem_Behavior import Problem_Behavior, Report_Warning
-from Standard.Table.Errors import Missing_Input_Columns, Column_Indexes_Out_Of_Range, Duplicate_Type_Selector
+from Standard.Table.Errors import Missing_Input_Columns, Column_Indexes_Out_Of_Range, Duplicate_Type_Selector, No_Index_Set_Error, No_Such_Column_Error
 import Standard.Table.Data.Match_Columns
 
 import Standard.Table.Data.Column_Name_Mapping
@@ -238,18 +238,34 @@ type Table
     ## Returns the column with the given name.
 
        Arguments:
-       - name: The name of the column being looked up.
+       - selector: The name or index of the column being looked up.
 
        > Example
          Get the names of all of the items from the shop inventory.
 
              import Standard.Examples
 
              example_at = Examples.inventory_table.at "item_name"
-    at : Text -> Column ! No_Such_Column_Error
-    at self name = case self.java_table.getColumnOrIndexByName name of
-        Nothing -> Error.throw (No_Such_Column_Error name)
-        c -> Column.Column c
+
+       > Example
+         Get the last column.
+
+             import Standard.Examples
+
+             example_at = Examples.inventory_table.at -1
+    at : Text | Integer -> Column ! No_Such_Column_Error | Index_Out_Of_Bounds_Error
+    at self selector=0 = case selector of
+        Integer ->
+            java_columns = Vector.Vector self.java_table.getColumns
+            Column.Column (java_columns.at selector)
+        Text ->
+            case self.java_table.getColumnOrIndexByName selector of
+                Nothing -> Error.throw (No_Such_Column_Error selector)
+                c -> Column.Column c
+
+    ## Returns the number of columns in the table.
+    column_count : Integer
+    column_count self = self.java_table.getColumns.length
 
     ## Returns a new table with a chosen subset of columns, as specified by the
        `columns`, from the input table. Any unmatched input columns will be
@@ -495,7 +511,7 @@ type Table
                 Nothing -> Nothing
                 _ -> val.to_text
         new_names = self.columns.map mapper
-        self.take_end (self.length - 1) . rename_columns (Column_Name_Mapping.By_Position new_names) on_problems=on_problems
+        self.take_end (self.row_count - 1) . rename_columns (Column_Name_Mapping.By_Position new_names) on_problems=on_problems
 
     ## ALIAS group, summarize
 
@@ -892,17 +908,6 @@ type Table
     row_count : Integer
     row_count self = self.java_table.rowCount
 
-    ## Returns the number of rows in this table.
-
-       > Example
-         Count the number of rows in the table.
-
-             import Standard.Examples
-
-             example_length = Examples.inventory_table.length
-    length : Integer
-    length self = self.row_count
-
     ## Returns a Table describing this table's contents.
 
        The table lists all columns, counts of non-null items and storage types
@@ -1140,33 +1145,6 @@ type Table
     to_csv : Text
     to_csv self = Text.from self (File_Format.Delimited delimiter=",")
 
-
-## UNSTABLE
-
-   An error returned when a non-existent column is being looked up.
-
-   Arguments:
-   - column_name: The name of the column that doesn't exist.
-type No_Such_Column_Error column_name
-
-## UNSTABLE
-
-   Create a human-readable version of the no such column error.
-No_Such_Column_Error.to_display_text : Text
-No_Such_Column_Error.to_display_text self =
-    "The column " + self.column_name + " does not exist."
-
-## UNSTABLE
-
-   An error returned when getting an index but no index is set for that table.
-type No_Index_Set_Error
-
-## UNSTABLE
-
-   Create a human-readable version of the no such column error.
-No_Index_Set_Error.to_display_text : Text
-No_Index_Set_Error.to_display_text self = "The table does not have an index set."
-
 ## UNSTABLE
 
    An error returned when the table contains no rows.

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

@@ -219,3 +219,29 @@ Column_Name_Mismatch.handle_java_exception =
         cause = caught_panic.payload.cause
         Error.throw (Column_Name_Mismatch (Vector.Vector cause.getMissing) (Vector.Vector cause.getExtras) cause.getMessage)
     Panic.catch ColumnNameMismatchException handler=throw_column_name_mismatch
+
+## UNSTABLE
+
+   An error returned when a non-existent column is being looked up.
+
+   Arguments:
+   - column_name: The name of the column that doesn't exist.
+type No_Such_Column_Error column_name
+
+## UNSTABLE
+
+   Create a human-readable version of the no such column error.
+No_Such_Column_Error.to_display_text : Text
+No_Such_Column_Error.to_display_text self =
+    "The column " + self.column_name + " does not exist."
+
+## UNSTABLE
+
+   An error returned when getting an index but no index is set for that table.
+type No_Index_Set_Error
+
+## UNSTABLE
+
+   Create a human-readable version of the no such column error.
+No_Index_Set_Error.to_display_text : Text
+No_Index_Set_Error.to_display_text self = "The table does not have an index set."

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

@@ -4,6 +4,7 @@ import Standard.Geo.Geo_Json
 import Standard.Table.IO.File_Read
 import Standard.Table.IO.File_Format
 import Standard.Table.IO.Excel
+import Standard.Table.Errors
 import Standard.Table.Data.Table
 import Standard.Table.Data.Column
 
@@ -13,7 +14,8 @@ export Standard.Table.Data.Column
 export Standard.Table.IO.File_Read
 export Standard.Table.IO.File_Format
 
-from Standard.Table.Data.Table export new, from_rows, join, concat, No_Such_Column_Error, Table
+from Standard.Table.Data.Table export new, from_rows, join, concat, Table
+from Standard.Table.Errors export No_Such_Column_Error
 
 ## ALIAS To Table
 

distribution/lib/Standard/Test/0.0.0-dev/src/Main.enso

@@ -743,7 +743,7 @@ fail_match_on_unexpected_error error frames_to_skip =
     payload = error.catch
     loc = Meta.get_source_location 1+frames_to_skip
     msg = "An unexpected dataflow error (" + payload.to_text + ") has been matched (at " + loc + ")."
-    fail msg
+    fail msg+'\n'+error.get_stack_trace_text
 
 
 ## PRIVATE