Create abstract Node model

src/main/kotlin/dsl/ast/node/Node.kt

@@ -0,0 +1,36 @@
+package dsl.ast.node
+
+import dsl.token.model.entity.TokenPosition
+
+class NoneNode : Node(0, TokenPosition.NONE)
+
+abstract class Node(numberOfChildren: Int, val position: TokenPosition) {
+    protected var children: Array<Node> = Array(numberOfChildren) { NONE }
+
+    constructor(children: Array<Node>, position: TokenPosition) : this(children.size, position) {
+        this.children = children
+    }
+
+    operator fun get(index: Int) = children[index]
+
+    operator fun set(index: Int, value: Node) {
+        children[index] = value
+    }
+
+    fun pretty(prefix: String = "", last: Boolean = true, first: Boolean = true) {
+        var newPrefix = prefix
+        var newLast = last
+        val newFirst = first
+
+        println(newPrefix + (if (newFirst) "" else if (newLast) "└─" else "├─") + this::class.simpleName + " " + position)
+        newPrefix += if (newLast) "   " else "│  "
+        for((index, child) in children.withIndex()) {
+            newLast = index == children.size - 1
+            child.pretty(newPrefix, newLast, false)
+        }
+    }
+
+    companion object {
+        val NONE = NoneNode()
+    }
+}