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remove some casts in AndThen #3518

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merged 1 commit into from
Jul 13, 2020
Merged

remove some casts in AndThen #3518

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43 changes: 16 additions & 27 deletions core/src/main/scala/cats/data/AndThen.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ package data

import java.io.Serializable
import cats.arrow.{ArrowChoice, CommutativeArrow}
import scala.annotation.tailrec

/**
* A function type of a single input that can do function composition
Expand Down Expand Up @@ -87,25 +88,19 @@ sealed abstract class AndThen[-T, +R] extends (T => R) with Product with Seriali
}

private def runLoop(start: T): R = {
var self: AndThen[Any, Any] = this.asInstanceOf[AndThen[Any, Any]]
var current: Any = start.asInstanceOf[Any]
var continue = true

while (continue) {
@tailrec
def loop[A, B](self: AndThen[A, B], current: A): B =
self match {
case Single(f, _) =>
current = f(current)
continue = false
case Single(f, _) => f(current)

case Concat(Single(f, _), right) =>
current = f(current)
self = right.asInstanceOf[AndThen[Any, Any]]
loop(right, f(current))

case Concat(left @ Concat(_, _), right) =>
self = left.rotateAccum(right)
loop(left.rotateAccum(right), current)
}
}
current.asInstanceOf[R]

loop(this, start)
}

final private def andThenF[X](right: AndThen[R, X]): AndThen[T, X] =
Expand All @@ -115,21 +110,15 @@ sealed abstract class AndThen[-T, +R] extends (T => R) with Product with Seriali

// converts left-leaning to right-leaning
final protected def rotateAccum[E](_right: AndThen[R, E]): AndThen[T, E] = {
var self: AndThen[Any, Any] = this.asInstanceOf[AndThen[Any, Any]]
var right: AndThen[Any, Any] = _right.asInstanceOf[AndThen[Any, Any]]
var continue = true
while (continue) {
self match {
case Concat(left, inner) =>
self = left.asInstanceOf[AndThen[Any, Any]]
right = inner.asInstanceOf[AndThen[Any, Any]].andThenF(right)

case _ => // Single
self = self.andThenF(right)
continue = false
@tailrec
def loop[A, B, C](left: AndThen[A, B], right: AndThen[B, C]): AndThen[A, C] =
left match {
case Concat(left1, right1) =>
loop(left1, Concat(right1, right))
case notConcat => Concat(notConcat, right)
}
}
self.asInstanceOf[AndThen[T, E]]

loop(this, _right)
}

override def toString: String =
Expand Down