56 Extension functions

The extension's first parameter acts as a receiver in text.bracketed(). It changes call syntax; it does not add stored state to String.

extension String bracketed(String text) {
  return "[" + text + "]"
}

String label(String text) {
  return text.bracketed()
}

main() {
  printLine(label(text: "Norm"))
  printLine("agent".bracketed())
}

Expected output:

[Norm]
[agent]

Try it: Call bracketed with an empty string.

Precise rules: Reference.