fold
abstract suspend fun <B> fold(recover: suspend (R) -> B, transform: suspend (A) -> B): B
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Runs the suspending computation by creating a Continuation, and running the fold function over the computation.
When the Effect has shifted with R it will recover the shifted value to B, and when it ran the computation to completion it will transform the value A to B.
import arrow.core.continuations.effect
import io.kotest.matchers.shouldBe
suspend fun main() {
val shift = effect<String, Int> {
shift("Hello, World!")
}.fold({ str: String -> str }, { int -> int.toString() })
shift shouldBe "Hello, World!"
val res = effect<String, Int> {
1000
}.fold({ str: String -> str.length }, { int -> int })
res shouldBe 1000
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open suspend fun <B> fold(error: suspend (error: Throwable) -> B, recover: suspend (R) -> B, transform: suspend (A) -> B): B
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Like fold but also allows folding over any unexpected Throwable that might have occurred.