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> You can see that there is no way to evaluate `x1` without first evaluating `m 1`, even if the result is a thunk. Isn't this true of `f(g(x))` as well? You ca

• jmillikin 4y ago
  Yep[0], and if you really wanted to, you could use that syntax to express the monadic interface: putStrLn :: TheWorld -> String -> (TheWorld, ()) main :: TheWorld -> (TheWorld, ()) main world = (part3, ()) where (part1, _) = putStrLn world "Hello" (part2, _) = putStrLn part1 ", " (part3, _) = putStrLn part2 "world!" It would be a frustrating user experience, but it's a valid and equivalent encoding to Haskell's `IO` type. [0] I'm ignoring lazy evaluation for now, but `f` could be implemented such that it returns before `g(x)` is evaluated. This is generally not relevant for purely functional code, but it can affect performance and exception-safety.
  • afiori 4y ago
    Lazy evaluation is exactly why Haskell has monads and Ocaml does not. the whole point of haskell was to see what happens if try to build a language with the strong requirement of lazy evaluation. If you remove it you also remove any need* for the IO monad * you can obviously use an IO like interface in a non-lazy language, but it is not necessary