Never used monads with Clojure (the only Lisp I've done "serious" work in). Haskell introduced them to me, but I've never done anything large with Haskell (no jobs!). Scala, however, has monads via the cats or (more recently) the ZIO library and they work just fine there.

The main problem with Monads is you're almost always the only programmer on a team who even knows what a Monad is.

> The hard part is managing effects

You can say that again!

Right now I'm working in C#, so I wished my C# managed effects, but it doesn't. It's all left to the programmer.

So, do you mean like you have some big array, and you want to do something like this? (Below is not a real programming language.)

  for i in 0 to arr.len() {
      new_val = f(arr[i]);
      log("Changing {arr[i]} to {new_val}.\n");
      arr[i] = new_val;
  }

I haven't used Haskell in a long time, but here's a kind of pure way you might do it in that language, which I got after tinkering in the GHCi REPL for a bit. In Haskell, since you want to separate IO from pure logic as much as possible, functions that would do logging return instead a tuple of the log to print at the end, and the pure value. But because that's annoying and would require rewriting a lot of code manipulating tuples, there's a monad called the Writer monad which does it for you, and you extract it at the end with the `runWriter` function, which gives you back the tuple after you're done doing the computation you want to log.

You shouldn't use Text or String as the log type, because using the Writer involves appending a lot of strings, which is really inefficient. You should use a Text Builder, because it's efficient to append Builder types together, and because they become Text at the end, which is the string type you're supposed to use for Unicode text in Haskell.

So, this is it:

  import qualified Data.Text.Lazy as T
  import qualified Data.Text.Lazy.Builder as B
  import qualified Data.Text.Lazy.IO as TIO
  import Control.Monad.Writer
  
  mapWithLog :: (Traversable t, Show a, Show b) => (a -> b) -> t a -> Writer B.Builder (t b)
  mapWithLog f = mapM helper
    where
      helper x = do 
        let x' = f x
        tell (make x <> B.fromString " becomes " <> make x' <> B.fromString ". ")
        pure x'
      make x = B.fromString (show x)

  theActualIOFunction list = do
    let (newList, logBuilder) = runWriter (mapWithLog negate list)
    let log = B.toLazyText logBuilder
    TIO.putStrLn log
    -- do something with the new list...

So "theActualIOFunction [1,2,3]" would print:

  1 becomes -1. 2 becomes -2. 3 becomes -3.

And then it does something with the new list, which has been negated now.

Statistically most of ones coworkers will never have looked at and used to write actual code with a functional language, so it is understandable they don't get it. What makes me sad is the apparent unwillingness to learn such a thing and sticking with "everything must OOP" even in situations where it would be (with a little practice and knowledge in functional languages) simple to make it purely functional and make testing and parallelization trivial.

But that's the irony of it, they did abandon the for-loops!

Maps and folds and filters are everywhere now. Why? Because 'functional is good!' ... but why is functional good?

> Who is "we", what was the price, and what was the imagined reward?

Slow down and re-read.

>> You get: the knowledge that your function's output will only depend on its input.

>> You pay: you gotta stop using those for-loops and [i]ndexes, and start using maps, folds, filters etc.