From a003211a2c0ea6da4f1730b620e4713bd3ed7fe7 Mon Sep 17 00:00:00 2001
From: Fedor Isakov <fisakov@gmail.com>
Date: Sat, 1 Aug 2020 15:12:44 +0200
Subject: [PATCH] Minor optimization of term trie.

---
 .../mps/logic/reactor/util/ArrayListStack.kt  |  5 +++-
 .../mps/logic/reactor/util/ClassicTermTrie.kt | 26 ++++++++++---------
 2 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/util/ArrayListStack.kt b/reactor/Core/src/jetbrains/mps/logic/reactor/util/ArrayListStack.kt
index e1e7df9b..131322aa 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/util/ArrayListStack.kt
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/util/ArrayListStack.kt
@@ -16,6 +16,9 @@
 
 package jetbrains.mps.logic.reactor.util
 
+import java.util.*
+import kotlin.collections.ArrayList
+
 /**
  * @author Fedor Isakov
  */
@@ -24,4 +27,4 @@ fun <T> ArrayList<T>.push (element: T): Unit { add(element) }
 
 fun <T> ArrayList<T>.pop (): T = removeAt(size - 1)
 
-fun <T> ArrayList<T>.peek (): T = last()
\ No newline at end of file
+fun <T> ArrayList<T>.peek (): T = get(size - 1)
diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/util/ClassicTermTrie.kt b/reactor/Core/src/jetbrains/mps/logic/reactor/util/ClassicTermTrie.kt
index 4dab8c4a..db27e3b7 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/util/ClassicTermTrie.kt
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/util/ClassicTermTrie.kt
@@ -76,41 +76,43 @@ class ClassicTermTrie<T> : TermTrie<T> {
         val seen = IdentityHashMap<Term, Term>()
         val nodeStack = arrayListOf(root)
         val termStack = arrayListOf(matchTerm)
+        val argPool = arrayListOf<Term>()
         while (!termStack.isEmpty()) {
             val node = nodeStack.peek()
             val term = termStack.pop()
 
             // dereferece the term only if it hasn't been dereferenced before
             val deref = deref(term).let { dt -> seen[dt]?.run { term } ?: dt.apply { seen[dt] = term } }
-            val arguments = deref.arguments().toList()
-            for(i in 1..arguments.size) {
-                termStack.push(arguments[arguments.size - i])
+            argPool.addAll(deref.arguments())
+            for(i in 1..argPool.size) {
+                termStack.push(argPool[argPool.size - i])
             }
-
-            val nextNode = node.nextOrDefault(symbolOrWildcard(deref)) { sym -> PathNode(sym, arguments.size) }
+            val nextNode = node.nextOrDefault(symbolOrWildcard(deref)) { sym -> PathNode(sym, argPool.size) }
             nodeStack.push(nextNode)
+            argPool.clear()
         }
 
         val head = nodeStack.pop()
         head.addValue(value)
-        nodeStack.reverse()
-        nodeStack.fold(head) { nextNode, node -> node.putNext(nextNode) }
+        nodeStack.foldRight(head) { node, nextNode  -> node.putNext(nextNode) }
     }
 
     private fun removeValue(matchTerm: Term, value: T) {
         val seen = IdentityHashMap<Term, Term>()
         val nodeStack = arrayListOf(root)
         val termStack = arrayListOf(matchTerm)
+        val argPool = arrayListOf<Term>()
         while (!termStack.isEmpty()) {
             val node = nodeStack.peek()
-            val term = termStack.removeAt(termStack.size - 1)
+            val term = termStack.pop()
 
             // dereferece the term only if it hasn't been dereferenced before
             val deref = deref(term).let { dt -> seen[dt]?.run { term } ?: dt.apply { seen[dt] = term } }
-            val arguments = deref.arguments().toList()
-            for(i in 1..arguments.size) {
-                termStack.add(arguments[arguments.size - i])
+            argPool.addAll(deref.arguments())
+            for(i in 1..argPool.size) {
+                termStack.push(argPool[argPool.size - i])
             }
+            argPool.clear()
 
             val nextNode = node.next(symbolOrWildcard(deref))
             if (nextNode == null)  {
@@ -251,7 +253,7 @@ class ClassicTermTrie<T> : TermTrie<T> {
             val term = ArrayList<PathNode<T>>()
             val edge = ArrayList<PathNode<T>>()
 
-            val stack = ArrayList<Pair<PathNode<T>, Int>>()
+            val stack = arrayListOf<Pair<PathNode<T>, Int>>()
             for (n in allNext()) {
                 stack.push(n to 0)
             }