type_varargs.kt

val validators = mapOf(
        String::class to { s: String -> s != "123" })

inline fun <vararg T, R> validate(vars: tuple<T>, action: (tuple<T>) -> R): R? =
        if (vars.all { validators(it::class)(it) })

            action(vars)
        else
            null

get("/methor") { request, _ ->

    validate(
            request.queryParams("key1"),
            request.queryParams("key2")) { (v1, v2) ->

        // do something
    }

}

inline fun <vararg T, R> guard(vars: tuple<T>, action: (tuple<T>) -> R): R? =
        if (vars.all { it != null })
            action(vars)
        else
            null

val sum = guard(1, 2, null) { (a, b, c) ->
    a+b+c
} ?: return null