As you say, it's just a matter of familiarity. Sounds like you just need exposure to more programming languages/paradigms, as it's a pretty common convention. I

As you say, it's just a matter of familiarity. Sounds like you just need exposure to more programming languages/paradigms, as it's a pretty common convention. I believe it comes from the ML family. OCaml[0] springs to mind. As others have mentioned, Rust[1], Kotlin[2], Haxe[3], Nim[4], Swift[5], Elm[6], Dhall[7], and Scala[8] all use this convention. The current syntax seems better for type inference and gradual typing. [0] https://learnxinyminutes.com/docs/ocaml/ https://learnxinyminutes.com/docs/ocaml/ [1] https://learnxinyminutes.com/docs/rust/ https://learnxinyminutes.com/docs/rust/ [2] https://learnxinyminutes.com/docs/kotlin/ https://learnxinyminutes.com/docs/kotlin/ [3] https://learnxinyminutes.com/docs/haxe/ https://learnxinyminutes.com/docs/haxe/ [4] https://learnxinyminutes.com/docs/nim/ https://learnxinyminutes.com/docs/nim/ [5] https://learnxinyminutes.com/docs/swift/ https://learnxinyminutes.com/docs/swift/ [6] https://learnxinyminutes.com/docs/elm/ https://learnxinyminutes.com/docs/elm/ [7] https://learnxinyminutes.com/docs/dhall/ https://learnxinyminutes.com/docs/dhall/ [8] https://learnxinyminutes.com/docs/scala/ https://learnxinyminutes.com/docs/scala/