Ada supports four forms of generic type definition in which a box appears ( shown as <>, that is the compound delimiter), it can be used as shown in the following examples.

generic

type Index is (<>); -- Discrete types

type Int is range <>; -- Integer types

type Angle is delta <>; -- Fixed point types

type Mass is digits <>; -- Floating point types

package Navigation_system is

----------

end Navigation_system;

The box construct provides reuser more flexibility over these type definitions.

Guideline1 : Provide reuser generic formal types with box definition for all scalar types, since it offers more flexibility and all predefined operations are available.