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Adding FP to the max implementation (#987)
* Adding an implementation of FP to the Max as an arrow example * Adding an implementation of FP to the Max as an arrow example Renaming a few things
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89
modules/docs/arrow-examples/src/test/kotlin/arrow/FpToTheMax.kt
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| Original file line number | Diff line number | Diff line change |
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| package arrow | ||
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| import arrow.core.Option | ||
| import arrow.core.Try | ||
| import arrow.effects.ForIO | ||
| import arrow.effects.IO | ||
| import arrow.effects.console | ||
| import arrow.effects.fRandom | ||
| import arrow.effects.fix | ||
| import arrow.effects.monad | ||
| import arrow.typeclasses.Monad | ||
| import arrow.typeclasses.binding | ||
| import java.util.Random | ||
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| /** | ||
| * This sample is a simple translation in Kotlin (using arrow, of course) of this talk: https://youtu.be/sxudIMiOo68 | ||
| */ | ||
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| object ORandom : Random() | ||
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| interface Console<F> { | ||
| fun putStrLn(s: String): Kind<F, Unit> | ||
| fun getStrLn(): Kind<F, String> | ||
| } | ||
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| @instance(IO::class) | ||
| interface IOConsoleInstance : Console<ForIO> { | ||
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| override fun putStrLn(s: String): Kind<ForIO, Unit> = IO { println(s) } | ||
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| override fun getStrLn(): Kind<ForIO, String> = IO { readLine().orEmpty() } | ||
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| } | ||
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| interface FRandom<F> { | ||
| fun nextInt(upper: Int): Kind<F, Int> | ||
| } | ||
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| @instance(IO::class) | ||
| interface FRandomInstance: FRandom<ForIO> { | ||
| override fun nextInt(upper: Int): Kind<ForIO, Int> = IO { ORandom.nextInt(upper) } | ||
| } | ||
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| class MonadAndConsoleRandom<F>(M: Monad<F>, C: Console<F>, R: FRandom<F>): Monad<F> by M, Console<F> by C, FRandom<F> by R { | ||
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| } | ||
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| object FpToTheMax { | ||
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| fun parseInt(s: String): Option<Int> = Try { s.toInt() }.toOption() | ||
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| fun <F> checkContinue(MC: MonadAndConsoleRandom<F>, name: String): Kind<F,Boolean> = MC.binding { | ||
| MC.putStrLn("Do you want to continue, $name?").bind() | ||
| val input = MC.getStrLn().map { it.toLowerCase() }.bind() | ||
| when (input) { | ||
| "y" -> MC.just(true) | ||
| "n" -> MC.just(false) | ||
| else -> checkContinue(MC, name) | ||
| }.bind() | ||
| } | ||
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| fun <F> gameLoop(MC: MonadAndConsoleRandom<F>, name: String): Kind<F, Unit> = MC.binding { | ||
| val num = MC.nextInt(5).map { it + 1 }.bind() | ||
| MC.putStrLn("Dear $name, please guess a number from 1 to 5:").bind() | ||
| val input = MC.getStrLn().bind() | ||
| parseInt(input).fold({ MC.putStrLn("You did not enter a number")}){ guess -> | ||
| if (guess == num) MC.putStrLn("You guessed right, $name!") | ||
| else MC.putStrLn("You guessed wrong, $name! The number was: $num") | ||
| }.bind() | ||
| val cont = checkContinue(MC, name).bind() | ||
| (if (cont) gameLoop(MC, name) else MC.just(Unit)).bind() | ||
| } | ||
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| fun <F> fMain(MC: MonadAndConsoleRandom<F>): Kind<F, Unit> = MC.binding { | ||
| MC.putStrLn("What is your name?").bind() | ||
| val name = MC.getStrLn().bind() | ||
| MC.putStrLn("Hello $name, welcome to the game").bind() | ||
| gameLoop(MC, name).bind() | ||
| } | ||
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| @JvmStatic | ||
| fun main(args: Array<String>) { | ||
| val r = fMain(MonadAndConsoleRandom(IO.monad(), IO.console(), IO.fRandom())) | ||
| r.fix().unsafeRunSync() | ||
| } | ||
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| } |