Re: [Boost-users] using transform_iterator with std::lower_bound

From: chun ping wang (cablepuff_at_[hidden])
Date: 2008-02-05 08:09:03

I am willing ot help out but i don't guaranteed i could make it on time..
like yesterday i got back around 7:50ish ... and sometimes i come back at
8:20 to 8:30 so under mine.. make sure you put someone as backup...

In Christ,
Chun.

On Feb 4, 2008 9:05 PM, Alexis H. Rivera-Rios <ahrivera_at_[hidden]> wrote:

> Hi,
>
> I'm trying to use a transform iterator and lower_bound
> to search a list of integers as if it was list of
> booleans.
>
> According to the message the const_mem_fun_ref_t
> doesn't have a default constructor. Is there a way to
> make this code compile?
>
> Your help will be appreciated!
> Alex
>
> #include<functional>
> #include <vector>
> #include <algorithm>
> #include <boost/iterator/transform_iterator.hpp>
>
> class T
> {
> public:
>        int _a;
>        T(int a) : _a(a) {}
>        bool greaterZero() const { return _a > 0; }
> };
>
> int main(void)
> {
>        typedef std::vector<T> Tlist;
>        typedef std::const_mem_fun_ref_t<bool,T> Function;
>    typedef boost::transform_iterator<Function,
>
> Tlist::const_iterator> Iterator;
>
>        Tlist x;
>        Iterator
> b(x.begin(),std::mem_fun_ref<bool,T>(&T::greaterZero)),
>
> e(x.end(),std::mem_fun_ref<bool,T>(&T::greaterZero));
>
>
>        std::lower_bound(b,e,false);
> }
>
>
> Error log:
> BD Software STL Message Decryptor v3.10 for gcc 2/3/4
> matob.cpp:28:2: warning: no newline at end of file
> /cygdrive/c/opt/boost_1_34_1/boost/iterator/transform_iterator.hpp:
> In
>    constructor
>   `boost::transform_iterator<
>        main()::Function, vector<T>::const_iterator,
> boost::use_default
>      , boost::use_default
>    >::transform_iterator()':
> stl_algo.h:2627:   instantiated from
>   `boost::transform_iterator<
>        main()::Function, vector<T>::const_iterator,
> boost::use_default
>      , boost::use_default
>    > lower_bound(
>        boost::transform_iterator<
>            main()::Function,
> vector<T>::const_iterator, boost::use_default
>          , boost::use_default
>        >, boost::transform_iterator<
>            main()::Function,
> vector<T>::const_iterator, boost::use_default
>          , boost::use_default
>        >, const bool &
>    )'
> matob.cpp:26:   instantiated from here
> /cygdrive/c/opt/boost_1_34_1/boost/iterator/transform_iterator.hpp:100:
> error:
>    No match for `const_mem_fun_ref_t<bool,
> T>::const_mem_fun_ref_t()'
> stl_function.h:640: candidates are:
> const_mem_fun_ref_t<bool, T>
>    ::const_mem_fun_ref_t(const
> const_mem_fun_ref_t<bool, T> &)
> stl_function.h:644:  const_mem_fun_ref_t<
>        bool, T>::const_mem_fun_ref_t(bool (T::*)()
> const)
>
>
>
> Programming Tutorial:
> In Python: To do this, do this
> In Perl: To do this, do this or this or this or this...
> In C: To do this, do this, but be careful
> In C++: To do this, do this, but don't do this, be careful of this, watch
> out for this, and whatever you do, don't do this
>
>
>
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