Subtype or derived type?

Subtype or derived type?

[Victor Porton]

While developing (thick object oriented) bindings for a C library:

I have developed a package containing Term_Type type with bindings
for raptor_term type:
https://github.com/vporton/redland-bindings/blob/ada2012/ada/src/rdf-raptor-term.ads

Term_Type represents pointer C type raptor_term* (where raptor_term
is a struct).

Now I am developed bindings for librdf_node which is defined as:

typedef raptor_term librdf_node;

Now I ask advice how to define the type representing librdf_node*
pointer type.

I have two variants in mind:

1.

subtype Node_Type is Term_Type;

2.

type Node_Type is new Term_Type;

Please advise which of the two is better.

-- 
Victor Porton - http://portonvictor.org

Re: Subtype or derived type?

[Victor Porton]

Victor Porton wrote:

> While developing (thick object oriented) bindings for a C library:
> 
> I have developed a package containing Term_Type type with bindings
> for raptor_term type:
> https://github.com/vporton/redland-bindings/blob/ada2012/ada/src/rdf-raptor-term.ads
> 
> Term_Type represents pointer C type raptor_term* (where raptor_term
> is a struct).
> 
> Now I am developed bindings for librdf_node which is defined as:
> 
> typedef raptor_term librdf_node;
> 
> Now I ask advice how to define the type representing librdf_node*
> pointer type.
> 
> I have two variants in mind:
> 
> 1.
> 
> subtype Node_Type is Term_Type;
> 
> 2.
> 
> type Node_Type is new Term_Type;
> 
> Please advise which of the two is better.

I am declined to use a derived type, because I may naturally have 
subprograms with the same name (as the name is derived from the name of the 
corresponding C function) and then using subtype, when I "use" both modules, 
the names would clash.

But I am not sure.

-- 
Victor Porton - http://portonvictor.org

Re: Subtype or derived type?

[Victor Porton]

Victor Porton wrote:

> Victor Porton wrote:
> 
>> While developing (thick object oriented) bindings for a C library:
>> 
>> I have developed a package containing Term_Type type with bindings
>> for raptor_term type:
>> https://github.com/vporton/redland-bindings/blob/ada2012/ada/src/rdf-raptor-term.ads
>> 
>> Term_Type represents pointer C type raptor_term* (where raptor_term
>> is a struct).
>> 
>> Now I am developed bindings for librdf_node which is defined as:
>> 
>> typedef raptor_term librdf_node;
>> 
>> Now I ask advice how to define the type representing librdf_node*
>> pointer type.
>> 
>> I have two variants in mind:
>> 
>> 1.
>> 
>> subtype Node_Type is Term_Type;
>> 
>> 2.
>> 
>> type Node_Type is new Term_Type;
>> 
>> Please advise which of the two is better.
> 
> I am declined to use a derived type, because I may naturally have
> subprograms with the same name (as the name is derived from the name of
> the corresponding C function) and then using subtype, when I "use" both
> modules, the names would clash.

"declined" should be "inclined".

> But I am not sure.

-- 
Victor Porton - http://portonvictor.org

Re: Subtype or derived type?

[Randy Brukardt]

"Victor Porton" <porton@narod.ru> wrote in message 
news:orauq5$9tv$1@gioia.aioe.org...
...
> I have two variants in mind:
>
> 1.
>
> subtype Node_Type is Term_Type;
>
> 2.
>
> type Node_Type is new Term_Type;
>
> Please advise which of the two is better.

It depends on how you want to use the type/subtype, of course.

If you need overridding/overloading, then you probably want a new type (a 
derived type), so the compiler can differentiate. If you need to convert 
back and forth a lot, you probably want a subtype (so the conversions are 
implicit rather than explicit). And so on...

                            Randy.