Prof. Dave Mason, Chair of Computer Science at Toronto Metropolitan University, only uses two programming languages these days: Smalltalk and Rust.

Smalltalk is chosen for situations where productivity and speed of development are crucial. Rust is chosen for situations where performance and memory safety are crucial.

Smalltalk is most interesting because it is the most productive of all the major programming languages. Capers Jones in 2017 published a study that demonstrated the productivity of various programming languages. Here’s a graphic that compares some of the languages: