Or Atria's transducers library (a-la Clojure), which can be applied to collections but also to pushy things (e.g. boost.signals, rx.observables, etc.):

Code: https://github.com/Ableton/atria/tree/master/src/atria/xform...

CppCon 2015 session: http://sinusoid.es/talks/transducers-cppcon15/ https://www.youtube.com/watch?v=vohGJjGxtJQ