Re: Encapsulating Ada.Direct_IO

["Yannick Duchêne (Hibou57)" <yannick_duchene@yahoo.fr>]

Le Wed, 17 Nov 2010 05:44:49 +0100, Bryan <brobinson.eng@gmail.com> a  
écrit:
> Spec file:
> ...
> private
>   package Byte_IO is new Ada.Direct_IO(Character);
>   type File_Type is new Byte_IO.File_Type;
> end Big5_Text_IO;
> ======================
Why did you used a “type new” ? Unless you give some reason, subtype is  
better better here, as this avoid un-meaningful conversions every where.  
If the type was defined in the public part, the type-new would have make  
sense, but here it is defined in the private part, so no need to use  
type-new, unless you want to attach it some special invariants which are  
not part of the invariants of your Byte_IO.File_Type.

When you begin with Ada, you oftenly forget to make a good choice between  
type-new and subtype (probably because there is no such things with any  
other language). Always balance type-new and subtype and don't  
systematically use type-new all the way. Make choices with reasons.

-- 
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les chiens.

“I am fluent in ASCII” [Warren 2010]