Robin Milner (1934–2010) was a British computer scientist whose work on type systems, programming languages, and concurrency theory earned him the Turing Award. His ML language and type inference algorithm influence virtually every modern typed language.
LCF and ML
At the University of Edinburgh, Milner developed the LCF (Logic for Computable Functions) theorem prover. To implement it, he created ML as a metalanguage. ML’s type system ensured that proofs couldn’t be accidentally broken by ill-typed code.
Type Inference
Milner’s key insight was that types could be inferred automatically. The Hindley-Milner type inference algorithm provides complete type inference for polymorphic functions—the compiler can deduce all types without any annotations.
Pi-Calculus
Later in his career, Milner developed the pi-calculus, a theoretical framework for reasoning about concurrent and distributed systems. The pi-calculus influenced actor models and modern concurrent programming theory.
CCS
Before the pi-calculus, Milner created CCS (Calculus of Communicating Systems), another foundational model for concurrent processes. His work provided rigorous ways to reason about parallel computation.
Recognition
Milner received the Turing Award in 1991 for his work on ML and type inference. He was knighted in 2004 for his contributions to computer science. His theoretical work continues to influence practical programming language design.