Re: [boost] [relational] Relational Model Library

From: Larry Evans (cppljevans_at_[hidden])
Date: 2005-09-27 18:06:08

On 09/27/2005 05:05 PM, Calum Grant wrote:
> 
>>-----Original Message-----
> 
> 
>>[mailto:boost-bounces_at_[hidden]] On Behalf Of Larry Evans
>>
>>>Is there any interest in providing relational containers in Boost?  
>>>Are there any features/improvements you can suggest for RML?
>>
>>http://visula.org/relational/implementation.html contains:
>>
>>   The reason this has to be a macro is because it needs to work with
>>   names, not just types.  It was felt that the benefits of 
>>being able to
>>   write customer.name or customers.name instead of 
>>column<1>(customers)
>>   or col<1,1>() outweighs the inherent disadvantages of 
>>using a macro.
>>
>>why not use an enumerator:
>>
>>    column<name>(customers)
>>
>>instead of a number:
>>
>>    column<1>(customers)
>>
>>?  Would this eliminate the macro need?  
> 
> 
> An early RML did use tuples indexed in the way you describe.  I did use
> enums - writing magic numbers is very bad for readibility and
                   ^^^^^^^^^^^^^ I guess you mean an enumeration here?
> maintainability.  Personally I prefer to read
> 
> 	customers.name
> 
> instead of 
> 
> 	column<name>(customers)
> 
Well, how about:

       customers.get<name>()

IMO, that's only marginally more verbose and just as readable.

> There is also a big problem with enums - being able to associate the
> correct enum with the correct type.  I.e. the "name" column may be 2 for
> customers, and 3 for products.  So you really need
> column<customer_name>(customers) and column<product_name>(product).

Or, customers.get<customers::name>()

OK, that's a little less readable :( , but I guess you believe the
disadvantage of macro use is not as bad as the disadvantage of
prefixing customers:: to the enumerator.  I'm not that sure.