Ferry Van Doorn
Principal Developer at Coolblue
Enschede, Overijssel, Netherlands
Summary
🤩
Rockstar🎓
Top SchoolFerry Van Doorn is a Principal Developer with 12 years of professional experience, currently leading engineering efforts at Coolblue after a decade-long tenure there. He combines practical product engineering for distributed and embedded systems—built earlier at HOMA for smart grids and energy asset fleets—with deep formal-methods expertise demonstrated by sustained contributions to Lean and Coq mathematical libraries. His open-source work includes core back-end changes to the Lean theorem prover and mathlib, where he formalized advanced topics like measure theory, category theory, and numeric structures, showing fluency in both functional programming and abstract mathematics. Ferry has a Master’s in Computer Science from the University of Twente and a track record of refactoring foundational libraries (e.g., Int/Nat in mathlib4) to improve reliability and reuse. He bridges the gap between rigorous formal verification and production-grade distributed systems, often surfacing subtle structural improvements that reduce technical debt. Based in Enschede, he brings a rare combo of applied systems design and provable-correctness thinking to complex software challenges.
12 years of coding experience
18 years of employment as a software developer
Master’s Degree, Computer Science, Master’s Degree, Computer Science at University of Twente
English, Dutch
Github Skills (16)
category-theory10
mathematics10
slim10
theorem-proving10
functional-programming10
formal-verification10
t410
coq10
type-theory10
logical10
math10
symbolic-logic10
foundation10
logic10
coq-library9
Programming languages (18)
Github contributions (5)
leanprover-community/mathlib4
Nov 2021 - Jan 2023
The math library of Lean 4
Role in this project:
Back-end Developer
Back-end DeveloperContributions:511 reviews, 105 commits, 173 PRs in 1 year 2 months
Contributions summary:Ferry primarily worked on the math library of Lean 4, focusing on refactoring and extending the `Int` and `Nat` data structures. They moved integer notation to separate files, declared new notations, and optimized imports. Furthermore, the user implemented a flexible version of `Expr.replace` and added `to_additive` features to allow the automatic transport of theorems and definitions from a multiplicative theory to an additive theory.
maththeorem-provingcomputer-algebra-systemmathematicsin-progress
leanprover-community/mathlib3
Jan 2019 - Jan 2023
Lean 3's obsolete mathematical components library: please use mathlib4
Role in this project:Back-end Developer & Mathematician
Back-end Developer & MathematicianContributions:910 reviews, 536 commits, 344 PRs in 4 years 1 month
Contributions summary:Ferry's contributions primarily involved the formalization of mathematical concepts and structures within the Lean mathematical library `mathlib3`. Their commits focus on adding new definitions and lemmas to the library, notably related to real numbers, complex analysis, and the development of measure theory concepts. They implemented functions for interval integrals, and formulated concepts such as the `is_empty` typeclass and general properties about the nonnegative cone, as well as properties about the Borel space.
maththeorem-provingcomponents-librarymathematicsjavascript
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