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EvalTest.kt
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EvalTest.kt
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package arrow.core
import arrow.core.test.UnitSpec
import arrow.core.test.concurrency.SideEffect
import arrow.core.test.stackSafeIteration
import io.kotest.matchers.shouldBe
class EvalTest : UnitSpec() {
init {
testLaws(
/*FxLaws.suspended<EvalEffect<*>, Eval<Int>, Int>(Arb.int().map(Eval.Companion::now), Arb.int().map(Eval.Companion::now), Eval<Int>::equals, eval::invoke) {
it.bind()
},
FxLaws.eager<RestrictedEvalEffect<*>, Eval<Int>, Int>(Arb.int().map(Eval.Companion::now), Arb.int().map(Eval.Companion::now), Eval<Int>::equals, eval::eager) {
it.bind()
}*/
)
"should map wrapped value" {
val sideEffect = SideEffect()
val mapped = Eval.now(0)
.map { sideEffect.increment(); it + 1 }
sideEffect.counter shouldBe 0
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
mapped.value() shouldBe 1
sideEffect.counter shouldBe 2
mapped.value() shouldBe 1
sideEffect.counter shouldBe 3
}
"later should lazily evaluate values once" {
val sideEffect = SideEffect()
val mapped = Eval.later { sideEffect.increment(); sideEffect.counter }
sideEffect.counter shouldBe 0
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
}
"later should memoize values" {
val sideEffect = SideEffect()
val mapped = Eval.later { sideEffect.increment(); sideEffect.counter }.memoize()
sideEffect.counter shouldBe 0
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
}
"always should lazily evaluate values repeatedly" {
val sideEffect = SideEffect()
val mapped = Eval.always { sideEffect.increment(); sideEffect.counter }
sideEffect.counter shouldBe 0
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
mapped.value() shouldBe 2
sideEffect.counter shouldBe 2
mapped.value() shouldBe 3
sideEffect.counter shouldBe 3
}
"always should memoize values" {
val sideEffect = SideEffect()
val mapped = Eval.always { sideEffect.increment(); sideEffect.counter }.memoize()
sideEffect.counter shouldBe 0
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
}
"defer should lazily evaluate other Evals" {
val sideEffect = SideEffect()
val mapped = Eval.defer { sideEffect.increment(); Eval.later { sideEffect.increment(); sideEffect.counter } }
sideEffect.counter shouldBe 0
mapped.value() shouldBe 2
sideEffect.counter shouldBe 2
mapped.value() shouldBe 4
sideEffect.counter shouldBe 4
mapped.value() shouldBe 6
sideEffect.counter shouldBe 6
}
"defer should memoize Eval#later" {
val sideEffect = SideEffect()
val mapped = Eval.defer { sideEffect.increment(); Eval.later { sideEffect.increment(); sideEffect.counter } }.memoize()
sideEffect.counter shouldBe 0
mapped.value() shouldBe 2
sideEffect.counter shouldBe 2
mapped.value() shouldBe 2
sideEffect.counter shouldBe 2
mapped.value() shouldBe 2
sideEffect.counter shouldBe 2
}
"defer should memoize Eval#now" {
val sideEffect = SideEffect()
val mapped = Eval.defer { sideEffect.increment(); Eval.now(sideEffect.counter) }.memoize()
sideEffect.counter shouldBe 0
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
mapped.value() shouldBe 1
sideEffect.counter shouldBe 1
}
"flatMap should complete without blowing up the stack" {
val limit = stackSafeIteration()
val sideEffect = SideEffect()
val flatMapped = Eval.now(0).flatMap(recur(limit, sideEffect))
sideEffect.counter shouldBe 0
flatMapped.value() shouldBe -1
sideEffect.counter shouldBe limit + 1
}
}
private fun recur(limit: Int, sideEffect: SideEffect): (Int) -> Eval<Int> {
return { num ->
if (num <= limit) {
sideEffect.increment()
Eval.defer {
recur(limit, sideEffect).invoke(num + 1)
}
} else {
Eval.now(-1)
}
}
}
}