[MrManatee]

If I understood correctly, the article suggests that as a general principle you should replace your union types and case-by-case code with lambdas. I feel almost the opposite.

Article: "In functional programming, the use of lambdas allows us to propagate not merely a serialized version of our intentions, but our actual intentions!"

Counterpoint: The use of structured objects instead of black box lambdas allows us to do more than just evaluate them. For example, Redux gets a lot of power by separating JSON-like action objects from the reducer that carries out the action.

But let's take instead the article's example of case-insensitive string matching. One tricky case is that normalization can change the length of the string: we might want the german "ß" to match "SS". Sure, the lambda approach can handle that. But now suppose that we want a new function that gives the location of the first match. It should support the same case-sensitivity options (because why not?). But now there is no way to get the pre-normalization location, because we encoded our normalization as a black box function. Case-by-case code would have handled this easily.