83 Control flow in result builders

Only the selected if branch contributes an element. The for loop contributes one element per iteration, preserving order in the final result.

import std.build.BuildWith
import std.build.ResultBuilder

class Words implements ResultBuilder<String, String> {
  private String text = ""
  Void add(String value) { text = text + value }
  String finish() { text }
}

String words(@BuildWith(Words.class) Function<String()> content) { content() }

main() {
  printLine(words {
    if true { "a" } else { "wrong" }
    for letter : ["b", "c"] { letter }
  })
}

Expected output:

abc

Try it: Make the condition false and predict the resulting text.

Precise rules: Reference.