The methodology

Constructive Programming is a methodology for building complex software, inspired by constructive logic. It leverages the Curry–Howard–Lambek correspondence to scale software that is formally verifiable from the way it is written.

In practice, it is about the restrictions you impose on your code to make it easier to understand, maintain, and evolve. There are three starting criteria:

  • Referential Transparency — the same input always yields the same output.
  • Totality — every defined input produces a defined output.
  • Termination — every computation eventually finishes.

The methodology is the lens through which we read code, design APIs, and prepare a codebase to be co-piloted by LLMs. The Libraries page lists the OSS that puts the methodology into Scala practice, and the home page introduces Fixed — a new language being designed around the same principles.

The team

Rodolfo Hansen — Head of Construction

Rodolfo founded Constructive Programming and currently leads the practice. He’s been writing software professionally for more than two decades — across Scala, Rust, Haskell, Kotlin, JavaScript, and a number of paradigms — and has been a CTO, a founder, an engineering manager, and an IC at nearly every team scale below “100 engineers.” He is currently the main engineer behind the cats-eo library and is designing the new research language Fixed, based in the Netherlands, where he operates this consulting firm.

Earlier he was a Global Software Quality & Craftsmanship Expert at Royal Philips, developing static-analysis metrics around Total Program Cardinality and driving software-craftsmanship practice across Europe. Before that, he was a Software Development Manager at Otravo (Amsterdam) — three teams under his lead, machine-learning shipped to production, a core loading pipeline taken from eleven hours down to fifteen minutes, defect reports cut by a third. He was CTO of Bodireel (London), a health-and-fitness platform built on a stateless RESTful Scala backend with Angular and Xamarin clients — 100% uptime, P95 under 20 ms, and a 30% reduction in infrastructure cost.

His career as a builder of teams started in 2008 when he founded KindleIT Software Development in Santo Domingo. Over the next eight years his team shipped widely-used open-source infrastructure (the first App Engine Maven plugin), maintained an international client base, and kept turnover under 5% before he sold the company.

The thread through all of it: small, accountable, distributed teams delivering at web scale and web speed, and constantly asking what the type system could do to make wrong programs harder to write.

Find Rodolfo: LinkedIn · GitHub · Medium

Talks

  • Serialization & De-serialization without doing either — Scala Love, Warsaw, 2024. A novel use of polymorphic lenses, with code drawn from cats-eo.
  • Total Program Cardinality — Scala Love (online), 2023. A new code-quality metric grounded in counting the inhabitants of a program’s types.
  • Correct by Construction — Better, Faster, Forever (Philips Innovation), Bangalore, 2019. Introduction to constructive programming practices; panel on software-architecture principles.
  • Type Refinement in Scala — Amsterdam Scala Meetup, 2017. Optics from the perspective of object-oriented design.
  • Lenses, No Mutes — Barcamp PUCMM, Santiago, 2016. The same idea, earlier and friendlier.

Longer-form writing on these themes lives at rodolfohansen.medium.com.

Education

  • MSc, Mathematics — Instituto Tecnológico de Santo Domingo (INTEC), 2007. Real Analysis, then Topology and Category Theory pursued independently.
  • BSc, Computer Software Engineering — Universidad APEC, 2004. Full scholarship from a national competition.

More consultants — coming

Constructive Programming is a single-consultant practice today; we are selectively adding senior collaborators. If you work at the intersection of typed functional design, dependent / refinement types, and LLM-augmented engineering, and you want to take on client work under this banner, get in touch at consulting@constructive.dev.

Working with us

We work on architecture-review, fractional-advisory, embedded-IC, and workshops/training shapes — see the home page for the engagement bullets. We are available for select engagements; based in the Netherlands; comfortable with EU MSAs and standard NDAs.

The fastest path is booking a 30-minute scoping call on the calendar, or emailing consulting@constructive.dev to set one up.