4 ms·

If you want to keep everything pure and also reasonably efficient, I think you need a sophisticated type system and a good compiler to back you up, e.g. Haskell

• silentbicycle 18y ago
  Dude, you don't need a sophisticated type system to count the occurrences of the numbers 0 to 255. Talk about, "Let's Take a Trivial Problem and Make it Hard".
  • henning 18y ago
    For this trivial contrived situation, yes. For the general problem of doing things purely where you would otherwise use destructive updates, you need a type system that lets the compiler safely and correctly figure things out about your program. Sheesh.
    • silentbicycle 18y ago
      I agree that sometimes it helps to have the type system in non-trivial situations, but in OCaml, you could do this imperatively, keep the state change isolated to a specific function (or module), and still give it a pure functional interface. The type system would do the same checks, even. (It sounds like that's what happens with Haskell's Data.Array.Diff.) At the same time, many programs in the real world get by without sophisticated type systems. They're a great tool, but they're also probably vastly more useful in some problem domains than others. Same with OOP, constraints and backtracking, relational databases, etc. (That said, I would love to use an ML-like language as small & clean as Lua. Inferred, garbage-collected, recursive tagged-union types rule.)