Hello everyone, If we have the following in Groov...

# announcements

[GarouDan]

Hello everyone,

If we have the following in Groovy / Gradle:

Closure a = { /*...*/ }
Closure b = { /*...*/ }
Closure c = a << b

How can we do that in Kotlin? Merging closures or high order functions?

I’m trying something like:

val a : KotlinSourceSet.() -> Unit = {
    dependencies {
        implementation(kotlin("stdlib-js"))
    }
}

val b: KotlinSourceSet.() -> Unit = {
    dependencies {
        implementation(project(":common", "jvmApiDefault"))
    }
}

where the result that I expect is something like:

val c: KotlinSourceSet.() -> Unit = {
    dependencies {
        implementation(kotlin("stdlib-js"))

        implementation(project(":common", "jvmApiDefault"))
    }
}

But how can we properly create the variable c?

[streetsofboston]

You mean composition of lambdas/closures?

[streetsofboston]

If so, create a andThen or compose function, something like this:
infix fun <A, B, C> ((A) -> B).andThen(g: (B) -> C): (A) -> C = { a: A -> g(this(a)) }

val c = a andThen b

[GarouDan]

My real case is the following:

val a : KotlinSourceSet.() -> Unit = {
	dependencies {
		implementation(kotlin("stdlib-js"))
	}
}

val b: KotlinSourceSet.() -> Unit = {
	dependencies {
		implementation(project(":common", "jvmApiDefault"))
	}
}

val c: KotlinSourceSet.() -> Unit = {
	dependencies {
		implementation(kotlin("stdlib-js"))

		implementation(project(":common", "jvmApiDefault"))
	}
}

I’m needing this for a gradle script of mine.

Where c is the result that I’m expecting.

[GarouDan]

Thanks @streetsofboston, this is an intersting code. But it is a bit complicated for my current knowledge of composing functions. Do you think we can achieve the expected result with something similar?

[streetsofboston]

Just code it yourself for this particular use case:
val c : KotlinSourceSet.() -> Unit= { a(); b() }

Using andThen would be a generic solution for this

[GarouDan]

Hum, interesting. Thank you. I’ll try this solution and return 😃