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Comment by saghm | Hacker News Reader

Java has (limited) type inference now I think, right? Does this work for the example you gave?

    public class Main {
      public static void main(String[] args) {
        var add = x -> y -> x + y;
        var addFive = add.apply(5);
        int result = addFive.apply(3);  // Output will be 8
      }
    }

Still not great, but a lot better than the original IMO

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You need an helper method for that

    public class Main {
      private static <T,R> Function<T,R> fun(Function<T,R> function) {
        return function;
      }

      public static void main(String[] args) {
        var add = fun(x -> fun(y -> x + y));
        var addFive = add.apply(5);
        int result = addFive.apply(3);  // Output will be 8
      }
    }

Those helpers should be part of the JDK.

No, I don’t think that works. Last time I checked, type inference doesn‘t work for lambda expressions.

Part of the reason - I think - is that lambda expressions need to be boiled down to some concrete @FunctionaInterface interface. You can have arbitrarily many of these, all with the same signature and method name, so language doesn‘t know which to choose.

Throw a checked exception in there and it all goes to hell all over again.

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