Add new REPL API

libraries/scripting/common/src/kotlin/script/experimental/util/linkedSnippet.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.script.experimental.util
+
+interface LinkedSnippet<T> {
+    val previous: LinkedSnippet<T>?
+    fun get(): T
+}
+
+fun <T> LinkedSnippet<T>?.toList(): List<T> = toList { it }
+
+fun <T, R> LinkedSnippet<T>?.toList(mapper: (T) -> R): List<R> {
+    val res = ArrayList<R>()
+    var el = this
+
+    while (el != null) {
+        res.add(mapper(el.get()))
+        el = el.previous
+    }
+
+    res.reverse()
+    return res
+}
+
+fun <T> LinkedSnippet<T>?.get(): T? = this?.get()
+
+class LinkedSnippetImpl<T>(private val _val: T, override val previous: LinkedSnippetImpl<T>?) : LinkedSnippet<T> {
+    override fun get(): T = _val
+}
+
+fun <T> LinkedSnippetImpl<T>?.add(value: T) = LinkedSnippetImpl(value, this)