Hylo is a safe-by-default programming language based on value semantics and generic programming.  It is the newest in a generation of languages, including Swift and Rust, that can uphold the safety and local reasoning properties of pure functional programming while supporting in-place mutation—the hallmarks of Mutable Value Semantics (MVS).  Hylo’s design recognizes MVS as a necessary organizing principle for safety, correctness, and performance, and presents a value-oriented programming model that is simpler than the constrained reference model of Rust or the hybrid model of Swift.  Hylo generics, like those of Swift and Rust, are separately type-checked, and like Swift’s, can be separately compiled, but Hylo’s model aims to address some of Swift’s restrictions and surprising behaviors.  This talk will explain how MVS is expressed in Hylo and discuss our ongoing exploration of support for generic programming.

Dave Abrahams cut his teeth in programming language design working on the C++ standard, starting in 1997 with exception safety for its standard library.  During those 16 years he became obsessed with Alexander Stepanov’s work on Generic Programming and its foundation of value semantics. In 2013 he joined the Swift programming language team at Apple, where he pursued his obsessions through the design of Swift’s language and standard library.  After seven years at Apple, he joined Google Brain to work on Swift for TensorFlow where he explored differentiable programming and collaborated on formalizing of value semantics and its application to AI.  After a brief dalliance with the Carbon language, he joined Adobe, where he is now a principal scientist in the Software Technology Lab, whose mission is to improve the code programmers write through research, education, and tooling.