September 2017 Update

Task/Amb/Kotlin/amb.kotlin

@@ -0,0 +1,41 @@
+// version 1.1.3
+
+typealias Constraint<T> = (T, T) -> Boolean
+
+fun <T> amb(lists: List<List<T>>, res: MutableList<T>, cons: Constraint<T>): Boolean {
+    if (lists.isEmpty()) return true
+    if (lists[0].isEmpty()) return false
+    val z = res.size
+    for ((i, el) in lists[0].withIndex()) {
+        if (i == 0) res.add(el) else res[z] = el
+        if (z > 0 && !cons(res[z - 1], res[z])) continue
+        if (amb(lists.drop(1), res, cons)) return true
+    }
+    res.removeAt(z)
+    return false
+}
+
+fun main(args: Array<String>) {
+    val wordLists = listOf(
+        listOf("the", "that", "a"),
+        listOf("frog", "elephant", "thing"),
+        listOf("walked", "treaded", "grows"),
+        listOf("slowly", "quickly")
+    )
+    val res = mutableListOf<String>()
+    val cons: Constraint<String> = { x, y -> x.last() == y.first() }
+    if (amb(wordLists, res, cons))
+        println(res)
+    else
+        println("No solution found")
+    val numLists = listOf(
+        listOf(1, 2, 3),
+        listOf(7, 6, 4, 5)
+    )
+    val res2 = mutableListOf<Int>()
+    val cons2: Constraint<Int> = { x, y -> x * y == 8 }
+    if (amb(numLists, res2, cons2))
+        println(res2)
+    else
+        println("No solution found")
+}