Re: [Boost-users] [parameter] Return type dependent on parameter type?

1 Oct 2007


      on Sun Sep 30 2007, François Duranleau  wrote:
...
Hi!
I have a function like this:
template< typename Arg0 ,
           typename Arg1 ,
           ... >
Arg1 the_function( Arg0 arg0 , Arg1 arg1 , ... ) { ... }
The return type should be the same as one of its parameters, and all '...' 
are optional parameters. Is there a way to use BOOST_PARAMETER_FUNCTION in 
such a case? I didn't find anything in the documentation about it. I tried 
this:
BOOST_PARAMETER_NAME( (arg1 , kw) arg1 )
BOOST_PARAMETER_NAME( (arg2 , kw) arg2 )
BOOST_FUNCTION_PARAMETER(
     (kw::arg2::_) ,
     the_function ,
     kw ,
     (required (arg1 , *) (arg2 , *))
     (optional ...)
)
Try:

  BOOST_PARAMETER_NAME( (arg1 , kw) arg1 )
  BOOST_PARAMETER_NAME( (arg2 , kw) arg2 )

  BOOST_PARAMETER_FUNCTION(
       (arg1_type) ,
       the_function ,
       kw ,
       (required (arg1 , *) (arg2 , *))
       (optional ...)
  )
  {
      return arg1;
  }

See
http://boost.org/libs/parameter/doc/html/index.html#adding-type-requirements

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com

Re: [Boost-users] [parameter] Return type dependent on parameter type?

David Abrahams