Why Y? Deriving the Y Combinator in JavaScript…and two practical applications… The Y Combinator is an important result in theoretical computer science.1 In this essay, after a brief review of the work we’ve already done on the Mockingbird, we’ll derive the Why Bird, known most famously as the Y Combinator. The why bird provides all the benefits of the mockingbird, but allows us to write more idiomatic JavaScript. We’ll see that one of the ben
