John Hughes is a computer scientist at Chalmers University of Technology in Sweden, where his homepage lists him as a professor in the Computing Science department and a member of the Functional Programming Group. He has spent his career advocating for functional programming and building tools that put its ideas into practice.
Hughes is best known for the essay “Why Functional Programming Matters,” a hosted copy of which is available on his Chalmers page, which argued that features like higher-order functions and lazy evaluation are what make functional programs more modular and reusable than their imperative counterparts.
He is also a creator of QuickCheck, a property-based testing framework in which the programmer states general properties a program should satisfy and the tool generates many random test cases to try to falsify them. His homepage notes that he is CEO of Quviq AB, a company offering a commercial version of QuickCheck. Hughes was among the researchers involved in the design of the Haskell language.