// !LANGUAGE: +ProperIeee754Comparisons

fun equals1(a: Double, b: Double?) = a == b

fun equals2(a: Double?, b: Double?) = a!! == b!!

fun equals3(a: Double?, b: Double?) = a != null && a == b

fun equals4(a: Double?, b: Double?) = if (a is Double) a == b else null!!

fun equals5(a: Any?, b: Any?) = if (a is Double && b is Double?) a == b else null!!

fun equals6(a: Any?, b: Any?) = if (a is Double? && b is Double) a == b else null!!

fun equals7(a: Double?, b: Double?) = a == b

fun equals8(a: Any?, b: Any?) = if (a is Double? && b is Double?) a == b else null!!


fun box(): String {
    if (!equals1(-0.0, 0.0)) return "fail 1"
    if (!equals2(-0.0, 0.0)) return "fail 2"
    if (!equals3(-0.0, 0.0)) return "fail 3"
    if (!equals4(-0.0, 0.0)) return "fail 4"

    if (!equals5(-0.0, 0.0)) return "fail 5"
    if (!equals6(-0.0, 0.0)) return "fail 6"

    if (!equals7(-0.0, 0.0)) return "fail 7"

    if (!equals8(-0.0, 0.0)) return "fail 8"

    if (!equals8(null, null)) return "fail 9"
    if (equals8(null, 0.0)) return "fail 10"
    if (equals8(0.0, null)) return "fail 11"

    return "OK"
}