wtf-kotlin

Wtf.kt

package Wtf


// Primitives

operator fun Int.plus(that: String) = "$this$that"

operator fun String.plus(that: Int) = "$this$that"


// Dictionary

class Dictionary<K, V>(val pairs: Map<K, V>) {
    override fun toString() = "[object Object]"
}

fun <K, V> dictOf(vararg pairs: Pair<K, V>) = Dictionary<K, V>(mapOf(*pairs))


// Array

class Array<T>(val elements: kotlin.Array<out T>) {
    override fun toString() = elements.joinToString(",")
}

fun <T> arrayOf(vararg elements: T) = Array<T>(elements)


// Dict/Array operations

operator fun Array<*>.plus(that: Dictionary<*, *>) = "[object Object]"

operator fun Dictionary<*, *>.plus(that: Array<*>) = 0

WtfTests.kt

package Wtf

import junit.framework.TestCase

class WtfTests : TestCase() {
    fun testAddNumberToString() {
        assertEquals("12", 1 + "2")
    }

    fun testAddStringToNumber() {
        assertEquals("12", "1" + 2)
    }

    fun testCastEmptyDictToString() {
        val dict = dictOf<String, Int>()

        assertEquals("[object Object]", dict.toString())
    }

    fun testCastEmptyArrayToString() {
        val array = arrayOf<Int>()

        assertEquals("", array.toString())
    }

    fun testCastArrayToString() {
        val dict = arrayOf(1, 2, 3)

        assertEquals("1,2,3", dict.toString())
    }

    fun testAddArrayToDict() {
        val array = arrayOf<Int>()
        val dict = dictOf<String, Int>()

        assertEquals("[object Object]", array + dict)
    }

    fun testAddDictToArray() {
        val array = arrayOf<Int>()
        val dict = dictOf<String, Int>()

        assertEquals(0, dict + array)
    }
}