Subject: Re: [boost] [proto] Problems with operator <<
From: John Maddock (boost.regex_at_[hidden])
Date: 2011-08-25 11:57:53
>> To answer my own question - in case anyone else gets bitten by this -
>> the answer is you need to provide overloads with both const and
>> non-const reference RHS arguments to effectively hide the proto operator
>> versions.
>>
>> Still some hair left yours.... John.
>
> Why answer you own question when I answered it for you yesterday?
>
> http://article.gmane.org/gmane.comp.lib.boost.devel/222816
Strange... that was exactly the answer I needed but it didn't show up in my
inbox... would have saved me some time too :-(
> And I think you have a reason to actual disable proto's operators
> instead of just hide them. Check the msg I sent yesterday.
The thing is I need left and right shift to be protoized, but I also need to
be able to overload for stream out, I ended up with several overloads
looking like:
template <class Stream, class Backend>
typename enable_if<is_convertible<Stream*, std::ostream*>,
std::ostream&>::type operator << (Stream& os, big_number<Backend>& r)
Which did the trick, and preserve protos shift operators, while still
working with all stream types.
BTW I do specify a proto grammar, and only enable the operators I need on a
case by case basis, in this case though I would need to restrict the grammar
so that proto's shift operators are only enabled for RHS arguments of
integer type. Is that possible?
John.