Erlang is in many ways quite old though many of the problems for which it used are quite modern. The Erlang language and system was designed around a set of requirements for telecom systems. They were distributed, massively concurrent systems which had to scale with demand, be capable of handling massive peak loads and never fail. The Erlang concurrency and error-handling model was developed around these requirements. We will describe the development of the language and the design of systems based on the Erlang showing how well the functional paradigm suits attacking these types of problems. We will also look at the further development with the introduction of new languages in the Erlang environment - the Erlang ecosystem.

Types allow us to structure data to match the functional requirements of the problem we are trying to solve. But, in most languages, we end up choosing/building types that are the closest to our requirement. They don't exactly fit our bill, as a result of which, we write runtime code to enforce those conditions. Then we write tests because the compiler can't help us. Dependently Typed Languages like Idris allow us to encode a wide range of invariants into the type itself allowing us to possibly have zero runtime errors.