No. At school, my teacher said that functional languages needed to have the 4 following features: procedures as data, tail-recursion, closure, garbage collector

No. At school, my teacher said that functional languages needed to have the 4 following features: procedures as data, tail-recursion, closure, garbage collector. There are many other features that define families of functional languages. homoiconicity vs rich syntax. lazy vs strict evaluation. pure vs mutable. static vs dynamic typing. call/cc, macros, ...