eventmachine - failed to build the gem

While i was trying to install rails 4.0.0 beta.I got stuck up with eventmachine gem failing all the way.

/home/jude/.rbenv/versions/1.9.3-p0/bin/ruby /home/nthillaiarasu/.rbenv/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/eventmachine-0.12.10/ext/extconf.rb
checking for rb_trap_immediate in ruby.h,rubysig.h... no
checking for rb_thread_blocking_region()... yes
checking for inotify_init() in sys/inotify.h... yes
checking for writev() in sys/uio.h... yes
checking for rb_thread_check_ints()... yes
checking for rb_time_new()... yes
checking for sys/event.h... no
checking for epoll_create() in sys/epoll.h... yes
creating Makefile
---> ext/fastfilereader
/home/jude/.rbenv/versions/1.9.3-p0/bin/ruby /home/jude/.rbenv/versions/1.9.3-p0/lib/ruby/gems/1.9.1/gems/eventmachine-0.12.10/ext/fastfilereader/extconf.rb
creating Makefile
<--- ext/fastfilereader
<--- ext
---> lib
---> lib/evma
<--- lib/evma
---> lib/em
---> lib/em/protocols
<--- lib/em/protocols
<--- lib/em
<--- lib
---> ext
make
compiling ed.cpp
make: g++: Command not found

Later i looked on the site http://isitruby19.com/eventmachine, there bunch of people had the same problem.Then from the error logs, it seems g++ is needed.Then i installed g++ in my ubuntu 11.10.

Now eventmachine got installed successfully.