src/Pure/General/codepoint.scala

more robust, notably for Isabelle/MAWEN "polyminus.sml matchsub (?a * (?b - ?c)...";

/*  Title:      Pure/General/codepoint.scala
    Author:     Makarius

Unicode codepoints vs. Unicode string encoding.
*/

package isabelle


object Codepoint {
  def string(c: Int): String = new String(Array(c), 0, 1)

  private class Iterator_Offset[A](s: String, result: (Int, Text.Offset) => A) extends Iterator[A] {
    var offset = 0
    def hasNext: Boolean = offset < s.length
    def next(): A = {
      val c = s.codePointAt(offset)
      val i = offset
      offset += Character.charCount(c)
      result(c, i)
    }
  }

  def iterator_offset(s: String): Iterator[(Int, Text.Offset)] = new Iterator_Offset(s, (_, _))
  def iterator(s: String): Iterator[Int] = new Iterator_Offset(s, (c, _) => c)

  def length(s: String): Int = iterator(s).length

  object Metric extends Pretty.Metric {
    val unit = 1.0
    def apply(s: String): Double = length(s).toDouble
  }
}