Ada Programming/Delimiters/<>

The box <> is a placeholder for something not (yet) fully specified.

Contexts

type Some_Array is array (Positive range <>) of Some_Type;

Declare an array type with bounds known only at runtime.

type T (<>) is private;

generic
  type T is (<>);

It means that T must be a discrete type: either an enumeration, a range, or a modular type.

Some_Rec_Type'(others => <>);

generic
  with package P is new G
     (Param_1 => T,
      others => <>);