Grow your own language: The YAFL story


25. 10. 2021
18:00 – 19:30



Thákurova 9, Prague 6


It will not be taken.

Darius Blasband will tell the story of how he grew YAFL, a programming language, a quarter of a century ago and how he evolves it over time. It will describe the benefits but also the pitfalls. Last but not least, he will explain the connection with his company, Raincode. The lecture is held in English.

Talk abstract

This talk tells the rather uncommon story of the co-evolution of Darius’s company, Raincode, with a home-grown programming language, YAFL. The two are intimately intertwined: Raincode would crumble if YAFL were to disappear, and YAFL would have no reason to exist if Raincode were to stop its activities. 

YAFL is a strongly-typed object-oriented language originally designed and implemented a quarter of a century ago. The story starts with YAFL’s inception, its design, the motivations (including the usual fantasies of world domination) and the technical underpinnings and some key implementation decisions. 

The story is rooted in the real world, where pragmatics reign. Darius will argue that their design choices and implementation decisions have converged to give YAFL its true value and that the fruits of growing their own language are well worth the maintenance burden. 

The talk will argue that YAFL is a non-DSL and touch on the good ideas as well as the lousy ones. Darius will discuss how to evolve a language over time by judiciously adding, as well as removing, features. 

Above all, it is a story about people. The language designer, its implementors, its first users, even its customers are the main characters of this comedy. Their interplay sheds light on how languages are created and maintained.

Darius Blasband

Darius Blasband was born in 1965, and has a master’s degree and a PhD from the Université Libre de Bruxelles. His focus is legacy modernization, articulated around compilers for legacy languages. Darius is the founder and CEO of Raincode, the main designer and implementer of its core technology, an acclaimed speaker in academic and industrial circles. He is the author of “The Rise and Fall of Software Recipes” (ISBN-13: 978-9490783426), and together with Jan Vitek (from Programming Research Laboratory), he is the co-host of the soon-to-be-released podcast “We Speak Your Language”.

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