[titzer]

I agree with this article. Tuples nicely unified multiple return values and multiple parameters. FWIW Scala and Virgil both support the _ syntax for the placeholder in a partial application.

    def add(x: int, y: int) -> int { return x + y; }
    def add3 = add(_, 3);

Or more simply, reusing some built-in functions:

    def add3 = int.+(_, 3);

[ackfoobar]

As noted in the article:

> This feature does have some limitations, for instance when we have multiple nested function calls, but in those cases an explicit lambda expression is always still possible.

I've also complained about that a while ago https://news.ycombinator.com/item?id=35707689

---

The solution is to delimit the level of expression the underscore (or dollar sign suggested in the article) belongs to. In Kotlin they use braces and `it`.

    { add(it, 3) } // Kotiln
    add(_, 3) // Scala

Then modifying the "hole in the expression" is easy. Suppose we want to subtract the first argument by 2 before passing that to `add`:

    { add(subtract(it, 2), 3) } // Kotlin
    // add(subtract(_, 2), 3) // no, this means adding 3 to the function `add(subtract(_, 2)`
    x => { add(subtract(x, 2), 3) } // Scala

[titzer]

I think I like the explicit lambda better; I prefer to be judicious with syntactic sugar and special variable names.

    fun x => add(subtract(x, 2), 3) // Virgil

[ackfoobar]

Coming from Scala to Kotlin, this is what I thought as well. Seeing `it` felt very wrong, then I got used to it.

[titzer]

I don't mind adopting features from popular languages. (After all, Virgil using _ for partial application turned out to be a happy accident that aligned with Scala.) Adopting features that are popping up in other languages helps to reduce the explanation burden, but I'm not sure on this one. It took me about 10 years to finally settle on having `fun` as a keyword to introduce lambdas instead of the parser back-tracking madness that JS parsers do.