Re: [Boost-users] [xpressive] Using placeholder in semantic actions

Subject: Re: [Boost-users] [xpressive] Using placeholder in semantic actions
From: Symons, Greg - SSD (Greg.Symons_at_[hidden])
Date: 2008-09-04 13:14:19

Eric Niebler wrote:

[snip]

>
> Xpressive overloads operators to give the impression that your can use a
> placeholder<T> as a T. But xpressive cannot overload operator. to give
> the impression of data member access because in C++ you can't overload
> operator..

Oh yeah... that would do it:) I'm glad you saw that right away, 'cause it would've taken me forever to wade through the source to figure out what I was doing wrong.

> Try this instead...
>
>    xpressive::function<std::string ParsedUri::*>::type getHostname =
>        {&ParsedUri::hostname};
>
> Now in your semantic actions, instead of doing this:
>
>    [ result.hostname = host ]
>
> You can do this:
>
>    [ result->*getHostname() = host ]
>
> Xpressive overloads operator->*, which is the closest thing to operator..
>
> Note to self: it would be better if we could leave off the parens in the
> above, like this: [ result->*getHostname = host ]. There's always more
> to do.

Thanks for the tip, it worked perfectly! Oh, and being able to leave off the parens would definitely be cool. The more I use xpressive, the more I really come to like it:)

--
Greg Symons
Software Engineer
ITT Corporation Space Systems Division
greg.symons_at_[hidden]
[phone]
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