Boost.Phoenix: Provide access to thrown exception in catch handler

[Stuart Dootson <stuart.dootson@…>]

I've been using Phoenix (the one that came with 1.44 - that's Phoenix v2?) for a bit, as a Boost.Lambda replacement, mostly happily. But I've come across a scenario I don't think Phoenix caters for, namely accessing an exception from a catch_ body, something like this:

std::vector<std::string> errors;
using namespace boost::phoenix;
using namespace boost::phoenix::arg_names;
std::for_each(changes.begin(), changes.end(), 
   try_
   [
      bind(&SomeClass::AddChange, this, arg1, std::string())
   ]
   .catch_<std::runtime_error>()`
   [
      push_back(ref(errors), bind(&std::runtime_error::what, /* Can I access the exception that's been thrown? */))
   ]);

I want to aggregate any error information thrown by SomeClass::AddChange in the errors vector, to be rethrown after the for_each. In Boost.Lambda, I'd be able to use the _e placeholder to access the exception object, but there seems to be no way of doing so in Phoenix?

Adding a similar placeholder to give access to the exception object would be a very useful addition to Phoenix...

[Kohei Takahashi <flast@…>]

I implemented this feature and has been merged, see h ttps://github.com/boostorg/phoenix/pull/13.

[John Fletcher <J.P.Fletcher@…>]

This is now on develop. It has missed the cutoff for Boost 1.58.0 but will be in the next release of Boost. Thanks to Kohei Takakashi

[John Fletcher <J.P.Fletcher@…>]

Replying to John Fletcher <J.P.Fletcher@…>:

This is now on develop. It has missed the cutoff for Boost 1.58.0 but will be in the next release of Boost. Thanks to Kohei Takakashi

Sorry, that should be Kohei Takahashi.

[Braden McDaniel <braden@…>]

This doesn't appear to have made it into Boost 1.59.0, either.

[John Fletcher]

This has now been moved to master and so will be in 1.60.0