Joe Armstrong, who has died aged 68 from complications related to pulmonary fibrosis, was a computer scientist and one of the creators at Ericsson of the programming language Erlang, used by companies as diverse as Bet365, WhatsApp and Cisco. It was Joe’s idea to write a book on the language – Concurrent Programming in Erlang (co-authored with Michael Williams and Robert Virding, 1992) – rather than just an internal manual for the company, as a precursor to the language being…