Programming language features I like

• Lightweight namespaces (mod in Rust, module in OCaml)
  • This is one feature I really wish Python had.
• Algebraic data types with pattern matching (Rust, OCaml)
  • This is the other feature I really wish Python had.
• Option types instead of implicitly nullable types (Option in Rust, option in OCaml)
• Result types instead of exceptions (Result in Rust, Or_error.t in OCaml)
  • Rust's ? syntactic sugar makes them especially ergonomic.
  • (T, error) return types in Go are similar. Some don't like them; I still prefer them to exceptions.
• Lightweight named tuples (~x, ~y in [[OCaml]])
  • Great for return types of functions that don't warrant a full record type

Table stakes

• First-class syntax for looping over a sequence (e.g., for ... in in Python)
• Some kind of ternary conditional expression (cond ? x : y in [[C]], x if cond else y in Python, etc.)