Re: access-to-constant dispatching params

[Andy <andy@nospam.tj>]

m_cubed@my-deja.com wrote:
> 
> Ada provides access-to-variable dispatching
> parameters.
> 
> For example:
> 
> procedure Set_Exercise_Mode (
>   State_Ptr: access State_Type;
>   Exercise_Mode: in Exercise_Mode_Type);
> 
> What it doesn't seem to provide is
> access-to-constant dispatching parameters.
> It would be useful to be able to ensure that
> a query on an object is prevented from
> accidentally updating the object. For example,
> (in hypothetical syntax):
> 
> function Exercise_Mode (
>   State_Ptr: access constant State_Type)
>   return Exercise_Mode_Type;
> 

How about using an  in  parameter?

  function Exercise_Mode (
      State : in State_Type)
      return Exercise_Mode_Type;
 

If the code that uses this type are maintaining some sort of structure,
list or array of State_Type pointers, one can always dereference:


   Mode := Exercide_Mode (State =>  State_Ptr.all);

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Andy
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