Custom operator that can be used when constructing series from observations or frames from key-row or key-column pairs. The operator simply returns a tuple, but it provides a more convenient syntax. For example: series [ "k1" => 1; "k2" => 15 ] [category:Frame construction]

Custom operator that can be used when constructing a frame from observations of series. The operator simply returns a tuple, but it upcasts the series argument so you don't have to do manual casting. For example: frame [ "k1" =?> series [0 => "a"]; "k2" =?> series ["x" => "y"] ] [category:Frame construction]