Is it possible to avoid function names at all in Kotlin DSL?

Question

In Kotlin DSL example they use plus signs to implement raw content inserting:

html {
    head {
        title {+"XML encoding with Kotlin"}
    }
    // ...
}

Is it possible to define "nameless" functions in receiver to be able to write

html {
    head {
        title {"XML encoding with Kotlin"}
    }
    // ...
}

Are there any plans to do so in future versions of Kotlin?

Is there such things in languages, other than Kotlin?

Answer 1

I can think of two solutions to your problem:

1. Make the lambda with receiver return a String:

   fun title(init: Title.() -> String) {
       val t = Title().apply {
           children.add(TextElement(init()))
       }
       children.add(t)
   }
   

   You can now call the title as suggested in OP. Actually this seems to be overhead in this particular scenario though and I'd recommend the following.

2. Create another title method that takes a String directly:

   class Head : TagWithText("head") {
       fun title(init: Title.() -> Unit) = initTag(Title(), init)
       fun title(text: String) {
           val t = Title().apply {
               children.add(TextElement(text))
           }
           children.add(t)
       }
   }
   

   Used like this:

   head {
       title("XML encoding with Kotlin")
   }