Re: [Boost-users] using bind with find_if

Subject: Re: [Boost-users] using bind with find_if
From: Dennis Jones (djones_at_[hidden])
Date: 2011-03-09 21:36:40

"Igor R" <boost.lists_at_[hidden]> wrote in message 
news:AANLkTimdhsHw+Ow8VAfrNZQe=5g79R9KudWiokwN8a54_at_mail.gmail.com...
>> I just have to add:
>>
>> typedef bool result_type;
>>
>> to my functor, or call boost::bind<bool>.
>
> Or just define a simple function instead of the functor (which is
> stateless anyway).

Thanks for the suggestion.  However, this:

bool OverrideMatches(
    const TItemOverride &OverrideSource,
    const RecNo_t ChildItemRecNo,    <-- note: these are const
    const RecNo_t LinkItemRecNo )
{
  return
    OverrideSource.ChildAssyItemRecNo == ChildItemRecNo &&
    OverrideSource.LinkItemRecNo == LinkItemRecNo;
}

const RecNo_t ChildItemRecNo = 123;  <-- note: these are const too
const RecNo_t LinkItemRecNo = 456;

std::find_if(
    FOverridesContainer.begin(),
    FOverridesContainer.end(),
    boost::bind(OverrideMatches, _1, ChildItemRecNo, LinkItemRecNo) );

results in an error:

[C++ Error] bind_cc.hpp(50, 4): E2034 Cannot convert
'_bi::bind_t<bool,bool (*)(const TItemOverride &,const unsigned int,const 
unsigned int),_bi::list3<arg<1> (*)(),_bi::value<const unsigned 
int>,_bi::value<const unsigned int> > >' to
'_bi::bind_t<bool,bool (*)(const TItemOverride &,unsigned int,unsigned 
int),_bi::list3<arg<1> (*)(),_bi::value<const unsigned int>,_bi::value<const 
unsigned int> > >'

This is odd, because the arguments are const and the parameters in the 
function are declared as const.  It seems to me that it should compile, but 
doesn't.  Why not? (compiler bug?)  Now, if I remove the 'const' from the 
integer parameter declarations, or if I make them const references, it 
compiles fine.

- Dennis