Re: [boost] limited form of type deduction

From: Joel de Guzman (joel_at_[hidden])
Date: 2003-10-11 18:19:19

Paul Mensonides <pmenso57_at_[hidden]> wrote:
>> [mailto:boost-bounces_at_[hidden]] On Behalf Of Brian McNamara
> 
>>    typedef result_of< op_plus(int, double) >::type result;
>> 
>> would truly work.  (Names like op_plus are just used as tags
>> which stand for the corresponding C++ operators.)
> 
> Just for fun:
> 
> You can use a template to handle all operators:
> 
> template<int> struct op { };
> 
> typedef result_of< op<'+'>(int, double) >::type result;
> 
> The longest operator in C++ is 4 characters %:%: (i.e. token-pasting to
> the preprocessor).  Otherwise, core language (non-keyword) operators max
> out at three characters (e.g. >>=), so you should be able to fit all of
> them in an integer literal that has at least 4 bytes.
> 
> Of course, this doesn't work that great for postfix operators because
> there is no semantic difference, unless you fake it just like
> overloading it:
> 
> op<'++'>(Type)
> op<'++'>(Type, int)

Cool idea, Paul! I like it!

-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net