import com.dongxiguo.fastring.Fastring.Implicits._
def fast(a: Int) =
  fast"head ${
    (for (j <- 0 until 10 view) yield {
      fast"baz$j $a foo ${
        (for (i <- 0 until 4 view) yield {
          fast"$a i=$i"
        }).mkFastring(",")
      } bar\n"
    }).mkFastring("<hr/>")
  } tail"
fast(0).toString

def s(a: Int) =
  s"head ${
    (for (j <- 0 until 10 view) yield {
      s"baz$j $a foo ${
        (for (i <- 0 until 4 view) yield {
          s"$a i=$i"
        }).mkString(",")
      } bar\n"
    }).mkString("<hr/>")
  } tail"
s(0)

def sb(sb: StringBuilder, a: Int) {
  sb ++= "head "
  var first = true
  for (j <- 0 until 10 view) {
    if (first) {
      first = false
    } else {
      sb ++= ""<hr/>""
    }
    sb ++=
      "baz" ++= j.toString ++=
      " " ++= a.toString ++= " foo ";
    {
      var first = true
      for (i <- 0 until 4 view) {
        if (first) {
          first = false
        } else {
          sb ++= ","
        }
        sb ++= a.toString
        sb ++= " i="
        sb ++= i.toString
      }
    }
    sb ++= " bar\n"
  }
  sb ++= " tail"
  sb
}
val s = new StringBuilder
sb(s, 0)
s.toString

def f(a: Int) =
    f"head ${
      (for (j <- 0 until 10 view) yield {
        f"baz$j $a foo ${
          (for (i <- 0 until 4 view) yield {
            f"$a i=$i"
          }).mkString(",")
        } bar\n"
      }).mkString("<hr/>")
    } tail"
f(0)