Thanks for the help. I have another question though on a similar topic... Say I have a function: void deleter(B* b) { delete b; } and a list: std::list mylist; I can call the for_each algorithm on this list using my function above: std::for_each(mylist.begin(), mylist.end(), &deleter); and it will delete all of the objects pointed to in the list. Is it possible to convert deleter into a templated function: template<class T> void deleter(T* t) { delete t; } and pass that into the for_each algorithm? If so, How? Mark. Peter Dimov wrote:

From: "Mark Snelling"

...

Hello, I need some help using the boost::bind library. I have a map of objects with a string as the key eg map, what I want to do is call a member function on each Block* in the map using the std::for_each algorithm. The trivial solution would be to craft my own loop and iterate through the list calling the member function on each one. But I'm sure that the boost::bind library can help me out there.

class Block { public: void update(int x); };

void main() { map blocks; for_each(blocks.begin(), blocks.end(), *****); }

what should I replace the ***** with to call update() on each block?

std::for_each(blocks.begin(), blocks.end(), boost::bind(&Block::update, boost::bind(&std::map::value_type::second, _1), 5 ) );

if you insist. :-)

Another option:

template void for_each_pair(It first, It last, F f) { for(; first != last; ++first) { f(first->first, first->second); } }

int main() { std::map blocks; for_each_pair(blocks.begin(), blocks.end(), boost::bind(&Block::update, _2, 5)); }

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Thanks again Peter. The first solution was actually the one I was trying to compile but was getting linker errors trying to find the body of the concrete function (using MSVC 7) - wierd. Peter Dimov wrote:

From: "Mark Snelling" [...]

...

std::list mylist;

I can call the for_each algorithm on this list using my function above:

std::for_each(mylist.begin(), mylist.end(), &deleter);

and it will delete all of the objects pointed to in the list. Is it possible to convert deleter into a templated function:

template<class T> void deleter(T* t) { delete t; }

and pass that into the for_each algorithm?

Yes. You can use

std::for_each(mylist.begin(), mylist.end(), &deleter<Object>);

If this doesn't work, try

#include

std::for_each(mylist.begin(), mylist.end(), boost::checked_deleter<Object>());

An alternative is to convert mylist to

std::list< boost::shared_ptr<Object > mylist;

and let it worry about the lifetime of the objects.

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From: "Mark Snelling"

Ok, I understand the following:

std::for_each(mylist.begin(),mylist.end(),boost::checked_deleter<Object>());

But when I try to use the boost::checked_deleter on the objects held in a map using your solution to my first problem I don't seem to be able to get it to compile:

template void for_each_pair(It first, It last, F f) { for(; first != last; ++first) { f(first->first, first->second); } }

int main() { std::map blocks; std::for_each_pair(blocks.begin(), blocks.end(), boost::bind(boost::checked_delete<Block>(), _2)); }

checked_delete is a function template (no trailing 'r'); checked_deleter is a class template. :-) Also, on MSVC 6/7 you need to specify a return type when binding general function objects: boost::bind<void>(boost::checked_deleter<Block>(), _2)