From 4787237b315572dd356e89eb78e62376179faac8 Mon Sep 17 00:00:00 2001
From: "firepick1 (localhost)" <karl@firepick.org>
Date: Thu, 24 Aug 2017 20:18:06 -0700
Subject: [PATCH 1/3] #933 +unaryMinus to subtract

---
 lib/function/algebra/simplify/simplifyCore.js | 3 +++
 test/function/algebra/simplify.test.js        | 6 ++++++
 2 files changed, 9 insertions(+)

diff --git a/lib/function/algebra/simplify/simplifyCore.js b/lib/function/algebra/simplify/simplifyCore.js
index b290fafc1..2927b5bcf 100644
--- a/lib/function/algebra/simplify/simplifyCore.js
+++ b/lib/function/algebra/simplify/simplifyCore.js
@@ -49,6 +49,9 @@ function factory(type, config, load, typed, math) {
           if (type.isConstantNode(a1) && a1.value === "0") {
               return a0;
           }
+          if (type.isOperatorNode(a1) && a1.op === '-' && a1.fn === 'unaryMinus') {
+              return new OperatorNode('-', 'subtract', [a0,a1.args[0]]);
+          }
           return new OperatorNode(node.op, node.fn, a1 ? [a0,a1] : [a0]);
       } else if (node.op === "-") {
           if (type.isConstantNode(a0) && a1) {
diff --git a/test/function/algebra/simplify.test.js b/test/function/algebra/simplify.test.js
index 9e7c668bf..b0f64b30c 100644
--- a/test/function/algebra/simplify.test.js
+++ b/test/function/algebra/simplify.test.js
@@ -53,6 +53,12 @@ describe('simplify', function() {
     assert.equal(fsimplified.eval()(5), 0.9933071490757153);
   });
 
+  it('should simplifyCore convert +unaryMinus to subtract', function() {
+      var result = math.simplify('x + y + a', [math.simplify.simplifyCore], {a: -1}).toString()
+      assert.equal(result, "x + y - 1");
+  });
+
+
   it('should handle custom functions', function() {
     function doubleIt (x) { return x + x }
     var node = math.expression.node;

From e9fa99983f18bd83eac07d864d0b43b855345143 Mon Sep 17 00:00:00 2001
From: "firepick1 (localhost)" <karl@firepick.org>
Date: Thu, 24 Aug 2017 20:34:41 -0700
Subject: [PATCH 2/3] #933 nargs

---
 lib/function/algebra/simplify/simplifyCore.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/function/algebra/simplify/simplifyCore.js b/lib/function/algebra/simplify/simplifyCore.js
index 2927b5bcf..ee7af5d35 100644
--- a/lib/function/algebra/simplify/simplifyCore.js
+++ b/lib/function/algebra/simplify/simplifyCore.js
@@ -49,7 +49,7 @@ function factory(type, config, load, typed, math) {
           if (type.isConstantNode(a1) && a1.value === "0") {
               return a0;
           }
-          if (type.isOperatorNode(a1) && a1.op === '-' && a1.fn === 'unaryMinus') {
+          if (node.args.length === 2 && type.isOperatorNode(a1) && a1.op === '-' && a1.fn === 'unaryMinus') {
               return new OperatorNode('-', 'subtract', [a0,a1.args[0]]);
           }
           return new OperatorNode(node.op, node.fn, a1 ? [a0,a1] : [a0]);

From 5b175d56a51923c0efd2ac64e805bc70d3bfa0aa Mon Sep 17 00:00:00 2001
From: "firepick1 (localhost)" <karl@firepick.org>
Date: Mon, 28 Aug 2017 06:35:40 -0700
Subject: [PATCH 3/3] #934 unaryMinus simplifyCore

---
 lib/function/algebra/simplify/simplifyCore.js | 8 +++++++-
 test/function/algebra/simplify.test.js        | 3 ++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/lib/function/algebra/simplify/simplifyCore.js b/lib/function/algebra/simplify/simplifyCore.js
index ee7af5d35..987807da5 100644
--- a/lib/function/algebra/simplify/simplifyCore.js
+++ b/lib/function/algebra/simplify/simplifyCore.js
@@ -61,7 +61,7 @@ function factory(type, config, load, typed, math) {
                   return new OperatorNode("-", "unaryMinus", [a1]);
               }
           }
-          if (node.fn === "subtract") {
+          if (node.fn === "subtract" && node.args.length === 2) {
               if (type.isConstantNode(a1) && a1.value === "0") {
                   return a0;
               }
@@ -70,8 +70,14 @@ function factory(type, config, load, typed, math) {
               }
               return new OperatorNode(node.op, node.fn, [a0,a1]);
           } else if (node.fn === "unaryMinus") {
+              if (type.isOperatorNode(a0)) {
+                  if (a0.fn === 'unaryMinus') {
+                      return a0.args[0];
+                  }
+              }
               return new OperatorNode(node.op, node.fn, [a0]);
           }
+          throw new Error('never happens');
       } else if (node.op === "*") {
           if (type.isConstantNode(a0)) {
               if (a0.value === "0") {
diff --git a/test/function/algebra/simplify.test.js b/test/function/algebra/simplify.test.js
index b0f64b30c..838e02a1a 100644
--- a/test/function/algebra/simplify.test.js
+++ b/test/function/algebra/simplify.test.js
@@ -54,6 +54,7 @@ describe('simplify', function() {
   });
 
   it('should simplifyCore convert +unaryMinus to subtract', function() {
+      simplifyAndCompareEval('--2', '2');
       var result = math.simplify('x + y + a', [math.simplify.simplifyCore], {a: -1}).toString()
       assert.equal(result, "x + y - 1");
   });
@@ -143,9 +144,9 @@ describe('simplify', function() {
   });
 
   it('should collect separated like factors', function() {
+    simplifyAndCompare('x*y*-x/(x^2)', '-y');
     simplifyAndCompare('x/2*x', 'x^2/2');
     simplifyAndCompare('x*2*x', '2*x^2');
-    simplifyAndCompare('x*y*-x/(x^2)', '-y');
   });
 
   it('should handle non-existing functions like a pro', function() {