  Eff is a programming language based on the algebraic approach to
computational effects, in which effects are viewed as algebraic operations and
effect handlers as homomorphisms from free algebras. Eff supports first-class
effects and handlers through which we may easily define new computational
effects, seamlessly combine existing ones, and handle them in novel ways. We
give a denotational semantics of eff and discuss a prototype implementation
based on it. Through examples we demonstrate how the standard effects are
treated in eff, and how eff supports programming techniques that use various
forms of delimited continuations, such as backtracking, breadth-first search,
selection functionals, cooperative multi-threading, and others.
