Functional programming in C++ https://meetingcpp.com/tl_files/mcpp/2015/talks/Nicola%20Gigante%20-%20functionalcpp.handout%20-%20Meeting%20C++%202015.pdf http://modernescpp.com/index.php/the-definition-of-functional-programming http://blog.madhukaraphatak.com/functional-programming-in-c++/