Re: [boost] Re: mpl apply_if.hpp question

From: Aleksey Gurtovoy (agurtovoy_at_[hidden])
Date: 2004-10-13 19:26:34

Larry Evans writes:
> On 10/13/2004 01:56 PM, Aleksey Gurtovoy wrote:
> [snip]
>> Larry, this is not related to "apply_if" renaming, but rather to
>> changes
>> in the MPL's iterator protocol --
>> http://www.mywikinet.com/mpl/mpl_1_32_changelog/iterator-protocol.html.
>> In particular, every place where you're dereferencing MPL iterators
>> via
>> '::type' needs to be re-written using 'mpl::deref' metafunction, as per
>> cited document.
>> HTH,
>> --
>
> Thanks Aleksey.  However, following the first row in that table:
>
> Before          Now
> ------          ---
> i::type 	deref<i>::type
>
> I changed the toy example to:
>
> <------------------
> #include <boost/mpl/eval_if.hpp>
> #include <boost/mpl/deref.hpp>
> struct C
> {
>      static bool const value=true;
> };
> struct f1
> {};
> struct f2
> {};
> namespace boost{namespace mpl{
>
> typedef  deref<eval_if<C,f1,f2> >::type X;
> X x;

Oh, this is not at all what I meant. 'eval_if<C,f1,f2>' is not an
iterator.

>
> }}
>  >------------------
> and got this error:
> <------------------
> /home/evansl/prog_dev/boost-snapshot/boost-04-10-04-0600/boost/mpl/deref.hpp(30):
> error: class "boost::mpl::eval_if<C, f1, f2>" has no member "type"
>        typedef typename Iterator::type type;
>                                   ^
>            detected during instantiation of class
>            "boost::mpl::deref<Iterator> [with
>            Iterator=boost::mpl::eval_if<C, f1, f2>]" at line 13 of
>            "test.cpp"
>  >------------------
> Please let me know what else I should do.

If you provide me with the [location of the] code you're trying to
compile, I'll try to take a quick look at it.

-- 
Aleksey Gurtovoy
MetaCommunications Engineering