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Using State instead of StateT
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@diogocanut
diogocanut committed Aug 22, 2023
1 parent ecac102 commit 4d72a8b
Showing 1 changed file with 32 additions and 44 deletions.
76 changes: 32 additions & 44 deletions core/src/main/scala/cats/Monad.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -43,14 +43,12 @@ trait Monad[F[_]] extends FlatMap[F] with Applicative[F] {
*
* Example:
* {{{
* scala> import cats.{Id, Monad}
* scala> import cats.data.StateT
* scala> import cats.data.State
* scala> import cats.syntax.all._
* scala> val appendStr: StateT[Id, String, Unit] = StateT.modify(_ + "a")
* scala> val appendStrAndGet: StateT[Id, String, String] = appendStr *> StateT.get
* scala> val (result, agg) = appendStrAndGet.whileM[Vector](StateT.inspect(i => !(i.length >= 5))).run("")
* scala> val appendStr = State { i: String => (i+"a", i)}
* scala> val (result, agg) = appendStr.whileM[Vector](State.inspect(i => !(i.length >= 5))).run("").value
* result: String = aaaaa
* agg: Vector[String] = Vector(a, aa, aaa, aaaa, aaaaa)
* agg: Vector[String] = Vector("", a, aa, aaa, aaaa)
* }}}
*/

Expand All @@ -75,11 +73,10 @@ trait Monad[F[_]] extends FlatMap[F] with Applicative[F] {
*
* Example:
* {{{
* scala> import cats.{Id, Monad}
* scala> import cats.data.StateT
* scala> import cats.data.State
* scala> import cats.syntax.all._
* scala> val appendStr: StateT[Id, String, Unit] = StateT.modify(_ + "a")
* scala> val (result, _) = appendStr.whileM_(StateT.inspect(i => !(i.length >= 3))).run("")
* scala> val appendStr = State { i: String => (i+"a", i)}
* scala> val (result, _) = appendStr.whileM_(State.inspect(i => !(i.length >= 3))).run("").value
* result: String = aaa
* }}}
*/
Expand All @@ -105,14 +102,12 @@ trait Monad[F[_]] extends FlatMap[F] with Applicative[F] {
*
* Example:
* {{{
* scala> import cats.{Id, Monad}
* scala> import cats.data.StateT
* scala> import cats.data.State
* scala> import cats.syntax.all._
* scala> val increment: StateT[Id, Int, Unit] = StateT.modify(_ + 1)
* scala> val incrementAndGet: StateT[Id, Int, Int] = increment *> StateT.get
* scala> val (result, aggregation) = incrementAndGet.untilM[Vector](StateT.inspect(_ >= 5)).run(-1)
* scala> val increment = State { i: Int => (i+1, i)}
* scala> val (result, aggregation) = increment.untilM[Vector](State.inspect(_ >= 5)).run(-1).value
* result: Int = 5
* aggregation: Vector[Int] = Vector(0, 1, 2, 3, 4, 5)
* aggregation: Vector[Int] = Vector(-1, 0, 1, 2, 3, 4)
* }}}
*/
def untilM[G[_], A](f: F[A])(cond: => F[Boolean])(implicit G: Alternative[G]): F[G[A]] = {
Expand All @@ -126,11 +121,10 @@ trait Monad[F[_]] extends FlatMap[F] with Applicative[F] {
*
* Example:
* {{{
* scala> import cats.{Id, Monad}
* scala> import cats.data.StateT
* scala> import cats.data.State
* scala> import cats.syntax.all._
* scala> val increment: StateT[Id, Int, Unit] = StateT.modify(_ + 1)
* scala> val (result, _) = increment.untilM_(StateT.inspect(_ >= 5)).run(-1)
* scala> val increment = State { i: Int => (i+1, i)}
* scala> val (result, _) = increment.untilM_(State.inspect(_ >= 5)).run(-1).value
* result: Int = 5
* }}}
*/
Expand All @@ -145,13 +139,12 @@ trait Monad[F[_]] extends FlatMap[F] with Applicative[F] {
*
* Example:
* {{{
* scala> import cats.{Id, Monad}
* scala> import cats.data.StateT
* scala> import cats.data.State
* scala> import cats.syntax.all._
* scala> val increment: StateT[Id, Int, Unit] = StateT.modify(_ + 1)
* scala> val incrementAndGet: StateT[Id, Int, Int] = increment *> StateT.get
* scala> val (result, _) = incrementAndGet.iterateWhile(_ < 5).run(-1)
* result: Int = 5
* scala> val increment = State { i: Int => (i+1, i)}
* scala> val (result, agg) = increment.iterateWhile(_ < 5).run(-1).value
* result: Int = 6
* agg: Int = 5
* }}}
*/
def iterateWhile[A](f: F[A])(p: A => Boolean): F[A] =
Expand All @@ -165,13 +158,12 @@ trait Monad[F[_]] extends FlatMap[F] with Applicative[F] {
*
* Example:
* {{{
* scala> import cats.{Id, Monad}
* scala> import cats.data.StateT
* scala> import cats.data.State
* scala> import cats.syntax.all._
* scala> val increment: StateT[Id, Int, Unit] = StateT.modify(_ + 1)
* scala> val incrementAndGet: StateT[Id, Int, Int] = increment *> StateT.get
* scala> val (result, _) = incrementAndGet.iterateUntil(_ == 5).run(-1)
* result: Int = 5
* scala> val increment = State { i: Int => (i+1, i)}
* scala> val (result, agg) = increment.iterateUntil(_ == 5).run(-1).value
* result: Int = 6
* agg: Int = 5
* }}}
*/
def iterateUntil[A](f: F[A])(p: A => Boolean): F[A] =
Expand All @@ -185,13 +177,11 @@ trait Monad[F[_]] extends FlatMap[F] with Applicative[F] {
*
* Example:
* {{{
* scala> import cats.{Id, Monad}
* scala> import cats.data.StateT
* scala> import cats.data.State
* scala> import cats.syntax.all._
* scala> val increment: StateT[Id, Int, Unit] = StateT.modify(_ + 1)
* scala> val incrementAndGet: StateT[Id, Int, Int] = increment *> StateT.get
* scala> val (n, sum) = 0.iterateWhileM(s => incrementAndGet.map(_ + s))(_ < 5).run(0)
* n: Int = 3
* scala> val increment = State { i: Int => (i+1, i)}
* scala> val (n, sum) = 0.iterateWhileM(s => increment.map(_ + s))(_ < 5).run(0).value
* n: Int = 4
* sum: Int = 6
* }}}
*/
Expand All @@ -209,13 +199,11 @@ trait Monad[F[_]] extends FlatMap[F] with Applicative[F] {
*
* Example:
* {{{
* scala> import cats.{Id, Monad}
* scala> import cats.data.StateT
* scala> import cats.data.State
* scala> import cats.syntax.all._
* scala> val increment: StateT[Id, Int, Unit] = StateT.modify(_ + 1)
* scala> val incrementAndGet: StateT[Id, Int, Int] = increment *> StateT.get
* scala> val (n, sum) = 0.iterateUntilM(s => incrementAndGet.map(_ + s))(_ > 5).run(0)
* n: Int = 3
* scala> val increment = State { i: Int => (i+1, i)}
* scala> val (n, sum) = 0.iterateUntilM(s => increment.map(_ + s))(_ > 5).run(0).value
* n: Int = 4
* sum: Int = 6
* }}}
*/
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