Simon Peyton Jones

Abstract Haskell is an unusual survivor in the Darwinian landscape of programming languages: it is long-lived (36 years old), yet not mainstream; it is both a research platform and a production tool; it pushes the boundaries of what you can do with static…

Abstract This is a series of four tutorial-style lectures, given at the Oregon Programming Languages Summer School 2026.

Abstract Eight years ago Compiling without continuations introduced the idea of so-called join points as a powerful optimisation tool in a functional language compiler.

Abstract Inlining has been claimed to be the single most important optimization in Haskell, and also the optimization receiving the most attention.

Abstract The standard dual-numbers construction works well for forward-mode automatic differentiation (AD) and is attractive due to its simplicity; recently, it also has been adapted to reverse-mode AD, but practical performance, especially on array progr…

Abstract When people think of codes, coding, and computers, they often think of socially challenged nerds like me, writing “code” (whatever that might be) in a darkened basement, all soulless ones and zeros and glowing screens.

Abstract Functional programming languages encourage expressing large parts of a program as declarative data flow pipelines, free of side-effects such as shared mutable state.

Abstract We explore denotational interpreters: denotational semantics that produce coinductive traces of a corresponding small-step operational semantics.

Abstract Functional logic languages have a rich literature, but it is tricky to give them a satisfying semantics.

Abstract Haskell is a big language, so GHC’s type inference engine is also big: it consists of 50,000 lines of Haskell, and another 42,000 lines of comments.