An increasing number of programming language courses include content on type theory. But learning about type theory is hard: students must learn what constitutes a rigorous proof and how to construct one. We have designed the SASyLF proof assistant to help students learn to write proofs about programming languages. SASyLF allows students to write proofs in any text editor, using a syntax very similar to what is used in classrooms—ensuring that instructors need not spend a lot of time teaching details of the tool. SASyLF’s built-in support for variable binding, inherited from its LF foundations, avoids the need for students to learn arcane variable encodings and allows us to provide good error messages. We provide an overview of SASyLF’s design, plans to integrate it into a course and widely used textbook, and the feedback we’ve gotten from students so far.

Jonathan Aldrich is a Professor of Computer Science at Carnegie Mellon University. He teaches courses in programming languages, software engineering, and program analysis for quality and security. Prof. Aldrich directed CMU’s Software Engineering Ph.D. program from 2013-2019.

Dr. Aldrich’s research centers on programming languages and type systems that are deeply informed by software engineering considerations and human factors. His research contributions include verifying the correct implementation of an architectural design, modular formal reasoning about code, and API protocol specification and verification. His notable awards include an NSF CAREER award (2006), the Dahl-Nygaard Junior Prize (2007), the DARPA Computer Science Study Group, and an ICSE most influential paper award (2012). He served as general chair (2015), program chair (2017), and steering committee chair (2017-2019) of SPLASH and OOPSLA. Aldrich holds a bachelor’s degree in Computer Science from Caltech and a Ph.D. from the University of Washington.