Algebraic effects are a popular subclass of effects, but not all effects of use in programming (or worthy of study!) are algebraic. The simplest example is the

Algebraic effects are a popular subclass of effects, but not all effects of use in programming (or worthy of study!) are algebraic. The simplest example is the continuation effect. It's not immediately clear why this effect isn't algebraic (it's not even immediately clear what "algebraic" means) but suffice to say continuations are very weird and behave very differently from other effects. At the same time, they're very useful and are a useful part of someone's programming vocabulary.