KotlinF_ck.kt

fun Int.isZero() = this == 0
fun Int.lt(other: Int) = this < other
fun Int.lte(other: Int) = this <= other
fun Int.gt(other: Int) = this > other
fun Int.gte(other: Int) = this >= other

class KotlinF_ck {
  private var tokens = charArray()
  private var jumps = hashMapOf<Int, Int>()

  fun parse(src: String) {
    tokens = src.toCharArray()
    var starts = arrayListOf<Int>()

    tokens.withIndices().forEach { pair ->
      val (i, c) = pair

      when(c){
        '[' -> starts.add(i)
        ']' -> {
          val j = starts.last()
          jumps.put(j, i)
          jumps.put(i, j)
          starts.remove(starts.lastIndex)
        }
      }
    }
  }

  fun run() {
    var tape = arrayListOf<Int>()
    var programCounter = 0
    var cursor = 0

    while(programCounter < tokens.size) {
      when(tokens[programCounter]){
        'k' -> {
          if(tape.size lte cursor) { tape.add(0) }
          tape[cursor]++
        }
        'o' -> {
          if(tape.size lte cursor) { tape.add(0) }
          tape[cursor]--
        }
        't' -> print(tape[cursor].toInt().toChar())
        'l' -> null
        'i' -> cursor++
        'n' -> cursor--
        '[' -> {
          if(tape[cursor].isZero()){ programCounter = jumps[programCounter] }
        }
        ']' -> {
          if(!tape[cursor].isZero()){ programCounter = jumps[programCounter] }
        }
      }
      programCounter++
    }
  }
}