Re: [boost] proto::or_ arity

From: Eric Niebler (eric_at_[hidden])
Date: 2007-04-19 13:35:09

Larry Evans wrote:
> On 04/19/2007 11:46 AM, Eric Niebler wrote:
> [snip]
>> Oh! You're chaining or_'s together. Sure, that works. So for your 
>> initial state, all you need is a pattern that never matches anything. 
>> For that, you can use proto::not<proto::_>.
> 
> I couldn't get that to compile; however, proto::logical_not<proto::_>
> does.  Thanks.

proto::not_<> is a fairly recent addition. Be sure you're sync'ed up. 
logical_not<_> is certainly not what you want here. It will successfully 
match proto expressions such as !as_expr('a'). You want something that 
will never match anything. You could also use 
proto::if_<mpl::always<mpl::false_> >.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com