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package axle.algebra

import spire.algebra.Semigroup

object Semigroups {

//  implicit def IntSemigroup: Semigroup[Int] = new Semigroup[Int] {
//    def op(x: Int, y: Int) = x + y
//  }
//
//  implicit def LongSemigroup: Semigroup[Long] = new Semigroup[Long] {
//    def op(x: Long, y: Long) = x + y
//  }
//
//  def IntMultSemigroup: Semigroup[Int] = new Semigroup[Int] {
//    def op(x: Int, y: Int) = x * y
//  }
//
//  implicit def DoubleSemigroup: Semigroup[Double] = new Semigroup[Double] {
//    def op(x: Double, y: Double) = x + y
//  }

  implicit def StringSemigroup: Semigroup[String] = new Semigroup[String] {
    def op(x: String, y: String): String = x + y
  }

  implicit def ListSemigroup[A]: Semigroup[List[A]] = new Semigroup[List[A]] {
    def op(x: List[A], y: List[A]): List[A] = x ++ y
  }

  implicit def MapSemigroup[K, V: Semigroup]: Semigroup[Map[K, V]] = new Semigroup[Map[K, V]] {

    val vSemi = implicitly[Semigroup[V]]

    def op(x: Map[K, V], y: Map[K, V]): Map[K, V] =
      (x.keySet ++ y.keySet).map(k => {
        if (x.contains(k)) {
          if (y.contains(k)) { (k, vSemi.op(x(k), y(k))) }
          else { (k, x(k)) }
        } else {
          (k, y(k))
        }
      }).toMap

  }

//  implicit def Tuple2Semigroup[R: Semigroup, S: Semigroup]: Semigroup[(R, S)] = new Semigroup[(R, S)] {
//    def op(x: (R, S), y: (R, S)) = (x._1 |+| y._1, x._2 |+| y._2)
//  }
//
//  implicit def Tuple3Semigroup[R: Semigroup, S: Semigroup, T: Semigroup]: Semigroup[(R, S, T)] = new Semigroup[(R, S, T)] {
//    def op(x: (R, S, T), y: (R, S, T)) = (x._1 |+| y._1, x._2 |+| y._2, x._3 |+| y._3)
//  }
//
//  implicit def Tuple4Semigroup[R: Semigroup, S: Semigroup, T: Semigroup, U: Semigroup]: Semigroup[(R, S, T, U)] = new Semigroup[(R, S, T, U)] {
//    def op(x: (R, S, T, U), y: (R, S, T, U)) = (x._1 |+| y._1, x._2 |+| y._2, x._3 |+| y._3, x._4 |+| y._4)
//  }

}