Re: [Boost-users] [BLL] Problem with print vector elements.

12 Apr 2012


      On 04/12/2012 11:06 AM, mik wrote:
...
Hi,
I'm trying to use thew BLL for the first time and I've the following
program:
class Date
{
public:
    Date(long d): _lDate(d) {}
    long getDate() const { return _lDate; }
    [...]
private:
    long _lDate;
};
std::ostream&  operator<<(std::ostream&s, const Date&x)
{
    [...]
}
struct C
{
    C(long d): date(d) {}
    Date date;
};
int main()
{
    const C c(46000);
    std::cout<<  boost::bind(&C::date, boost::lambda::_1)(c)<<  std::endl;
std::vector<C>  cont(1, C(46000));
    std::for_each(cont.begin(), cont.end(), std::cout<<
boost::bind(&C::date, boost::lambda::_1));
return 0;
}
The first std::cout is ok. But for the second one nested int the for_each I
get this message error:
error C2679: binary '<<' : no operator found which takes a right-hand
operand of type 'boost::_bi::bind_t' (or there is no acceptable
conversion)
with
[
    R=const Date&,
    F=boost::_mfi::dm,
    L=boost::_bi::list1>
]
C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\INCLUDE\ostream(653):
could be 'std::basic_ostream<_Elem,_Traits>  &std::operator
<<(std::basic_ostream<_Elem,_Traits>  &,const
char *)' [found using argument-dependent lookup]
with
[
    _Elem=char,
    _Traits=std::char_traits<char>
]
Can you help me?
To be honest, I am surprised that the first cout expression works. 
Boost.Lambda placeholders don't match well with Boost.Bind.
If you meant boost::lambda::bind instead of boost::bind, the for_each 
should work, assuming you included the header defining the operator
overloads for BLL expressions.
Assuming that you really meant boost::bind, and instead of ::_1 you 
accidently wrote boost::lambda::_1, you are in trouble. Boost.Bind only
overloads the following operators:  !, ==, !=, <, <=, >, >=, &&, ||. 
Which is the reason your program didn't compile.
If you have more problems, please provide a complete testcase (i.e. with 
includes etc.)
...
Thank you,
     Mirko
**
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Re: [Boost-users] [BLL] Problem with print vector elements.

Thomas Heller