From 51ca0a9ae2c927bc9211e914166585b882c1f69c Mon Sep 17 00:00:00 2001
From: Danila Fedorin <danila.fedorin@gmail.com>
Date: Wed, 26 Jul 2017 17:26:26 -0700
Subject: [PATCH 1/2] Make some operator-related fields protected in TreeNode.
 This should allow for the implementation of toString in child nodes.

---
 src/org/nwapw/abacus/tree/TreeNode.java | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/org/nwapw/abacus/tree/TreeNode.java b/src/org/nwapw/abacus/tree/TreeNode.java
index 8540677..accdefa 100644
--- a/src/org/nwapw/abacus/tree/TreeNode.java
+++ b/src/org/nwapw/abacus/tree/TreeNode.java
@@ -13,7 +13,7 @@ public abstract class TreeNode {
     /**
      * The lexer used to lex tokens.
      */
-    private static Lexer<TokenType> lexer = new Lexer<TokenType>(){{
+    protected static Lexer<TokenType> lexer = new Lexer<TokenType>(){{
         register("\\+|-|\\*|/|^", TokenType.OP);
         register("[0-9]+(\\.[0-9]+)?", TokenType.NUM);
         register("[a-zA-Z]+", TokenType.WORD);
@@ -23,7 +23,7 @@ public abstract class TreeNode {
     /**
      * A map that maps operations to their precedence.
      */
-    private static HashMap<String, Integer> precedenceMap = new HashMap<String, Integer>(){{
+    protected static HashMap<String, Integer> precedenceMap = new HashMap<String, Integer>(){{
         put("+", 0);
         put("-", 0);
         put("*", 1);
@@ -33,7 +33,7 @@ public abstract class TreeNode {
     /**
      * A map that maps operations to their associativity.
      */
-    private static HashMap<String, OperatorAssociativity> associativityMap =
+    protected static HashMap<String, OperatorAssociativity> associativityMap =
             new HashMap<String, OperatorAssociativity>() {{
                 put("+", OperatorAssociativity.LEFT);
                 put("-", OperatorAssociativity.LEFT);
@@ -45,7 +45,7 @@ public abstract class TreeNode {
     /**
      * Comparator used to sort token types.
      */
-    private static Comparator<TokenType> tokenSorter = Comparator.comparingInt(e -> e.priority);
+    protected static Comparator<TokenType> tokenSorter = Comparator.comparingInt(e -> e.priority);
 
     /**
      * Tokenizes a string, converting it into matches

From c88a0cbdc512d72f9311f40d02d6802000d3e8eb Mon Sep 17 00:00:00 2001
From: Danila Fedorin <danila.fedorin@gmail.com>
Date: Wed, 26 Jul 2017 17:26:55 -0700
Subject: [PATCH 2/2] Implement toString in child nodes of TreeNode.

---
 src/org/nwapw/abacus/tree/NumberNode.java |  5 +++++
 src/org/nwapw/abacus/tree/OpNode.java     | 15 +++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/src/org/nwapw/abacus/tree/NumberNode.java b/src/org/nwapw/abacus/tree/NumberNode.java
index f88ef0a..41112e7 100644
--- a/src/org/nwapw/abacus/tree/NumberNode.java
+++ b/src/org/nwapw/abacus/tree/NumberNode.java
@@ -49,4 +49,9 @@ public class NumberNode extends TreeNode {
     public <T> T reduce(Reducer<T> reducer) {
         return reducer.reduceNode(this);
     }
+
+    @Override
+    public String toString() {
+        return number != null ? number.toString() : "null";
+    }
 }
diff --git a/src/org/nwapw/abacus/tree/OpNode.java b/src/org/nwapw/abacus/tree/OpNode.java
index 33ba805..8a399f7 100644
--- a/src/org/nwapw/abacus/tree/OpNode.java
+++ b/src/org/nwapw/abacus/tree/OpNode.java
@@ -88,4 +88,19 @@ public class OpNode extends TreeNode {
         T rightReduce = right.reduce(reducer);
         return reducer.reduceNode(this, leftReduce, rightReduce);
     }
+
+    @Override
+    public String toString() {
+        String leftString = left != null ? left.toString() : "null";
+        String rightString = right != null ? right.toString() : "null";
+
+        if(right != null && right instanceof OpNode){
+            if(TreeNode.precedenceMap.get(((OpNode) right).getOperation()) >
+                    TreeNode.precedenceMap.get(operation)) {
+                rightString = "(" + rightString + ")";
+            }
+        }
+        
+        return leftString + operation + rightString;
+    }
 }