Ada 2005 Reference Manual
6.7 Null Procedures
A null_procedure_declaration provides a shorthand to declare a procedure with an empty body.
Syntax
Static Semantics
A null_procedure_declaration declares a null procedure. A completion is not allowed for a null_procedure_declaration.
Dynamic Semantics
The execution of a null procedure is invoked by a subprogram call. For the execution of a subprogram call on a null procedure, the execution of the subprogram_body has no effect.
The elaboration of a null_procedure_declaration has no effect.
Examples
procedure Simplify(Expr : in out Expression) is null; -- see 3.9
-- By default, Simplify does nothing, but it may be overridden in extensions of Expression
-- By default, Simplify does nothing, but it may be overridden in extensions of Expression
