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6.7 Null Procedures

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A null_procedure_declaration provides a shorthand to declare a procedure with an empty body. 

Syntax

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null_procedure_declaration ::= 
   [overriding_indicator]
   procedure_specification is null;

Static Semantics

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A null_procedure_declaration declares a null procedure. A completion is not allowed for a null_procedure_declaration.

Dynamic Semantics

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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. 
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The elaboration of a null_procedure_declaration has no effect. 

Examples

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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

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