A Programming Language with Versions [pdf]

One thing I like in Slashdot compared to HN is how stories there always contain some abstract.

Here is the one from that dissertation, which sounds intriguing:

> While modern software development heavily relies on versioned packages, the concept of versions is rarely supported in the semantics of programming languages, resulting in bulky and unsafe software updates.

> The dissertation proposes a programming language that intrinsically supports versions. To establish a basis of finer-grained version control in language semantics, the author proposes a language called VL, with core calculus for supporting multiple versions, a compilation method to the core, and an inference algorithm determining the version of each expression.

> The author proved the type safety of the core calculus to guarantee consistent versions in a program. The author also implements VL, a minimal but adequate functional language that supports data structures and a module system, and conducts a case study involving the simultaneous use of multiple versions.