6.7 Null Procedures
Reason: There are no null functions because
the return value has to be constructed somehow; a function that always
raises Program_Error doesn't seem very useful or worth the complication.
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.
Ramification: Thus, a null procedure
is equivalent to the body
with the exception that a null procedure can
be used in place of a procedure specification.
Simplify(Expr : in out
Expression) is null
; -- see 3.9
-- By default, Simplify does nothing, but it may be overridden in extensions of Expression
Extensions to Ada 95
Extensions to Ada 2005
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe