fun main(args: Array<String>) {
    val str = "I am a string"

    str.run {
        // no lambda params, receiver is value type (String), returns Unit.
    }

    str.let {
        // lambda params are value type (String), no receiver, returns Unit.
    }

    str.apply {
        // no lambda params, receiver is value type (String), returns value type (String).
    }

    str.also {
        // lambda params are value type (String), no receiver, returns value type (String).
    }

    with(str) {
        // no lambda params, receiver is value type (String), returns Unit,
        // it does NOT an extension function though the receiver will be defined as a parameter.
    }
}