Re: [boost] [lambda] extension question

From: Jaakko Järvi (jarvi_at_[hidden])
Date: 2005-07-19 02:35:21

On Jul 18, 2005, at 6:19 PM, Brock Peabody wrote:
>
> When I try to compile my example in VC 7.1 I get an error that seems to
> indicate that the type being passed to the sig template is
> boost::tuples::null_type.  Everything works if I hardwire it like:
>
>    template <class T> struct sig { typedef std::string type; };
>

Yes, a null_type is passed to sig. This is because the signature of the 
zero argument
lambda function (in lambda_functor class) signature is instantiated 
always, regardless
of whether it is called or not. And there the argument list is just 
null_type.
Hence, the return type deduction is not allowed to cause a compilation 
error in the
case where the argument tuple to sig is null_type.

Best, Jaakko

> Any ideas?
>
> Thanks,
> Brock
>
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-- Jaakko Järvi, jarvi_at_[hidden]