Philip Wadler Style Guide⁠‍⁠​‌​‌​​‌‌‍​‌​​‌​‌‌‍​​‌‌​​​‌‍​‌​​‌‌​​‍​​​​​​​‌‍‌​​‌‌​‌​‍‌​​​​​​​‍‌‌​​‌‌‌‌‍‌‌​​​‌​​‍‌‌‌‌‌‌​‌‍‌‌​‌​​​​‍​‌​‌‌‌‌‌‍​‌​​‌​‌‌‍​‌‌​‌​​‌‍‌​‌​‌‌‌​‍​​‌​‌​​​‍‌‌‌​‌​‌‌‍​‌‌‌‌​​​‍‌​​​‌​‌‌‍‌​​​​‌‌‌‍​​​​‌‌‌‌‍​​​​‌​‌​‍​​​​​​‌‌⁠‍⁠

Overview

Philip Wadler is a principal designer of Haskell, contributor to Java generics, and the person who brought monads from category theory into practical programming. His famous paper "Propositions as Types" illuminates the deep connection between logic and computation.

Core Philosophy

"The essence of functional programming is that programs are built by composing functions."

"Monads are just monoids in the category of endofunctors."

"A monad is a way to structure computations."

Wadler sees programming as applied mathematics—types are propositions, programs are proofs, and monads are the universal pattern for composition.

Design Principles

1. Types Are Propositions: A type signature is a theorem; the implementation is its proof.