VList: Difference between revisions

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@@ Line 649: / Line 649: @@
 {{omit from|Openscad}}
 {{omit from|Tcl|You wouldn't do such a low-level data structure directly in Tcl normally}}
+=={{header|Kotlin}}==
+{{trans|Go}}
+<lang scala>// version 1.1.3
+class VList<T : Any?> {
+    private class VSeg {
+        var next: VSeg? = null
+        lateinit var ele: Array<Any?>
+    }
+    private var base: VSeg? = null
+    private var offset = 0
+    /* locate kth element */
+    operator fun get(k: Int): T {
+        var i = k
+        if (i >= 0) {
+            i += offset
+            var sg = base
+            while (sg != null) {
+                @Suppress("UNCHECKED_CAST")
+                if (i < sg.ele.size) return sg.ele[i] as T
+                i -= sg.ele.size
+                sg = sg.next
+            }
+        }
+        throw IllegalArgumentException("Index out of range")
+    }
+    /* add an element to the front of VList */
+    fun cons(a: T): VList<T> {
+        if (this.base == null) {
+            val v = VList<T>()
+            val s = VSeg()
+            s.ele = arrayOf<Any?>(a)
+            v.base = s
+            return v
+        }
+        if (this.offset == 0) {
+            val l2 = this.base!!.ele.size * 2
+            val ele = arrayOfNulls<Any>(l2)
+            ele[l2 - 1] = a
+            val v = VList<T>()
+            val s = VSeg()
+            s.next = this.base
+            s.ele = ele
+            v.base = s
+            v.offset = l2 - 1
+            return v
+        }
+        this.offset--
+        this.base!!.ele[this.offset] = a
+        return this
+    }
+    /* obtain a new VList beginning at the second element of an old VList */
+    fun cdr(): VList<T> {
+        if (base == null) throw RuntimeException("cdr invoked on empty VList")
+        offset++
+        if (offset < base!!.ele.size) return this
+        val v = VList<T>()
+        v.base = this.base!!.next
+        return v
+    }
+    /* compute the size of the VList */
+    val size: Int
+        get() {
+            if (base == null) return 0
+            return base!!.ele.size * 2 - offset - 1
+        }
+    override fun toString(): String {
+        if (base == null) return "[]"
+        var r = "[${base!!.ele[offset]}"
+        var sg = base
+        var sl = base!!.ele.sliceArray(offset + 1..base!!.ele.lastIndex)
+        while (true) {
+            for (e in sl) r += " $e"
+            sg = sg!!.next
+            if (sg == null) break
+            sl = sg.ele
+        }
+        return r + "]"
+    }
+    fun printStructure() {
+        println("Offset: $offset")
+        var sg = base
+        while (sg != null) {
+            println(sg.ele.contentToString())
+            sg = sg.next
+        }
+        println()
+    }
+}
+fun main(args: Array<String>) {
+    var v = VList<Int>()
+    println("Before adding any elements, empty VList: $v")
+    v.printStructure()
+    for (a in 6 downTo 1) v = v.cons(a)
+    println("Demonstrating cons method, 6 elements added: $v")
+    v.printStructure()
+    v = v.cdr()
+    println("Demonstrating cdr method, 1 element removed: $v")
+    v.printStructure()
+    println("Demonstrating size property, size = ${v.size}\n")
+    println("Demonstrating element access, v[3] = ${v[3]}\n")
+    v = v.cdr().cdr()
+    println("Demonstrating cdr method again, 2 more elements removed: $v")
+    v.printStructure()
+}</lang>
+{{out}}
+<pre>
+Before adding any elements, empty VList: []
+Offset: 0
+Demonstrating cons method, 6 elements added: [1 2 3 4 5 6]
+Offset: 1
+[null, 1, 2, 3]
+[4, 5]
+[6]
+Demonstrating cdr method, 1 element removed: [2 3 4 5 6]
+Offset: 2
+[null, 1, 2, 3]
+[4, 5]
+[6]
+Demonstrating size property, size = 5
+Demonstrating element access, v[3] = 5
+Demonstrating cdr method again, 2 more elements removed: [4 5 6]
+Offset: 0
+[4, 5]
+[6]
+</pre>
 =={{header|ooRexx}}==