put

abstract fun put(a: A): Kind<F, Unit>

Puts A in the MVar if it is empty, or blocks if full until the given value is next in line to be consumed by take.

import arrow.fx.*
import arrow.fx.extensions.io.async.async
import arrow.fx.extensions.io.monad.flatMap

fun main(args: Array<String>) {
//sampleStart
val mvar = MVar.factoryUncancellable(IO.async())

mvar.empty<Int>().flatMap { v ->
  v.put(5).flatMap {
    v.take()
  }
}.unsafeRunSync() == 5
//sampleEnd
}