Re: calling generic template function from template specialization

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Tue, 19 Feb 2008 02:30:30 -0800 (PST)

Message-ID:

<e23f2ad3-3b53-44a4-aabe-e256d9c90487@p73g2000hsd.googlegroups.com>

On Feb 18, 11:57 pm, johanatan <johana...@gmail.com> wrote:

I have two functions that are nearly identical (one validates
a row and one validates a table). Since a table is open-ended
(i.e., can have infinite rows) but a row is finite, there is
one addtional line of code in the ValidateRow func which
asserts that the row data has the appropriate number of cells.

I would like to make these a template function with a
specialization for the row that asserts the one extra
condition and then calls the generic template function. Is
this possible?

The usual solution would be to use traits. Something like:

    template< typename T >
    struct AdditionalValidations
    {
        static bool isOk( T const& ) { return true ; }
    } ;

    template<>
    struct AdditionalValidations< Row >
    {
        static bool isOk( Row const& row )
        {
            return row.size() == whatever ;
        }
    } ;

In your template function, you would add code like:

    if ( theUsualValidations( obj )
            && AdditionalValidations< T >::isOk( obj ) {
        // error handling...
    }

--
James Kanze (GABI Software) email:james.kanze@gmail.com
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