axle.IndexedCrossProduct.scala Maven / Gradle / Ivy

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package axle

import spire.implicits._
import spire.algebra.BooleanAlgebra

object IndexedCrossProduct {

  def apply[E](lists: Seq[IndexedSeq[E]]): IndexedCrossProduct[E] = new IndexedCrossProduct[E](lists)
}

class IndexedCrossProduct[E](lists: Seq[IndexedSeq[E]]) extends Iterable[Seq[E]] {

  val mults = lists.reverse.map(_.size).scanLeft(1)(_ * _).reverse

  val syze = mults.head

  val modulos = mults.tail

  def indexOf(objects: Seq[E]): Int = {
    val mults = lists.zip(objects).map(lo => lo._1.indexOf(lo._2)).zip(modulos).map(im => im._1 * im._2)
    if (axle.forall(mults)(_ >= 0)) {
      mults.sum
    } else {
      -1
    }
  }

  def apply(i: Int): Seq[E] =
    lists.zip(modulos).foldLeft((i, List[E]()))(
      (cr, lm) => (cr._1 % lm._2, lm._1(cr._1 / lm._2) :: cr._2))._2.reverse

  override def size: Int = syze

  def iterator: Iterator[Seq[E]] = (0.until(size)).iterator.map(this(_))

}