Does Ada have automatic constructors and destructors?
(Tucker Taft replies) At least in Ada 9X, functions with controlling results are inherited (even if overriding is required), allowing their use with dynamic binding and class-wide types. In most other OOPs, constructors can only be called if you know at compile time the “tag” (or equivalent) of the result you want. In Ada 9X, you can use the tag determined by the context to control dispatching to a function with a controlling result.
Yes, controlled types have special, user-definable operations that control the construction and destruction of objects and values of those types (see question 8.1, above). (Also: Tucker Taft replies) At least in Ada 95, functions with controlling results are inherited (even if overriding is required), allowing their use with dynamic binding and class-wide types. In most other OOPs, constructors can only be called if you know at compile time the “tag” (or equivalent) of the result you want. In Ada 95, you can use the tag determined by the context to control dispatching to a function with a controlling result.
Yes, controlled types have special, user-definable operations that control the construction and destruction of objects and values of those types (see question 8.1, above). (Also: Tucker Taft replies) At least in Ada 9X, functions with controlling results are inherited (even if overriding is required), allowing their use with dynamic binding and class-wide types. In most other OOPs, constructors can only be called if you know at compile time the “tag” (or equivalent) of the result you want. In Ada 9X, you can use the tag determined by the context to control dispatching to a function with a controlling result. For example: type Set is abstract tagged private; function Empty return Set is abstract; function Unit_Set(Element : Element_Type) return Set is abstract; procedure Remove(S : in out Set; Element : out Element_Type) is abstract; function Union(Left, Right : Set) return Set is abstract; …
In Ada 95, functions with controlling results are inherited (even if overriding is required), allowing their use with dynamic binding and class-wide types. In most other OOPs, constructors can only be called if you know at compile time the “tag” (or equivalent) of the result you want. In Ada 95, you can use the tag determined by the context to control dispatching to a function with a controlling result. For example: type Set is abstract tagged private; function Empty return Set is abstract; function Unit_Set(Element : Element_Type) return Set is abstract; procedure Remove(S : in out Set; Element : out Element_Type) is abstract; function Union(Left, Right : Set) return Set is abstract; … procedure Convert(Source : Set’Class; Target : out Set’Class) is — class-wide “convert” routine, can convert one representation — of a set into another, so long as both set types are — derived from “Set,” either directly or indirectly. — Algorithm: Initialize Target to the empty set, and then — c
