Re: [Boost-users] [boost-users][lambda] crash in std::for_each

Subject: Re: [Boost-users] [boost-users][lambda] crash in std::for_each
From: Stuart Dootson (stuart.dootson_at_[hidden])
Date: 2009-02-03 09:22:08

On Tue, Feb 3, 2009 at 9:45 AM, Igor R <boost.lists_at_[hidden]> wrote:
> The following code crashes in for_each when trying to output the 1st pair.
> What's wrong with it?
>
> Thanks!
>
> namespace bl = boost::lambda;
> std::map<std::string, std::string> temp;
> temp["a"] = "1";
> temp["b"] = "2";
> const std::map<std::string, std::string> attrs(temp);
> typedef std::pair<std::string, std::string> string_pair;
> std::stringstream stream;
> std::for_each(attrs.begin(), attrs.end(),
>    stream << bl::bind(&string_pair::first, bl::_1)
> << bl::bind(&string_pair::second, bl::_1));

Try changing the string_pair typedef to:

 std::pair<std::string const, std::string> string_pair;

Not 100% sure *why* this makes it run rather than crash (with VC++
2008, Boost 1.37.0), but it makes some sort of sense, as the key in a
map is immutable.

Stuart Dootson