feat: support negation sign (-)

bump version to 1.1.0

dist/index.js

@@ -154,10 +154,12 @@ var parseExpression = function parseExpression(expression) {
 
   // Create an array of separated numbers & operators
   while (stream.next()) {
-    var cur = stream.current();
+    var cur = stream.current(),
+        past = stack.length - 1;
     if (cur === ' ') {
       continue;
     }
+
     // it's probably a function with a length more than one
     if (!_.isNumber(cur) && !_operators2['default'][cur] && cur !== '.') {
       record += cur;
@@ -167,6 +169,19 @@ var parseExpression = function parseExpression(expression) {
     } else if (_.isNumber(stack[stack.length - 1]) && (_.isNumber(cur) || cur === '.')) {
 
       stack[stack.length - 1] += cur;
+    } else if (stack[past] === '-') {
+      var beforeSign = stack[stack.length - 2];
+
+      if (_operators2['default'][beforeSign]) {
+        stack[past] += cur;
+      } else if (beforeSign === ')') {
+        stack[past] = '+';
+        stack.push('-' + cur);
+      } else if (_.isNumber(beforeSign)) {
+        stack.push(cur);
+      } else {
+        stack[past] += cur;
+      }
     } else {
       stack.push(cur);
     }

dist/tests/basic.js

@@ -1,73 +0,0 @@
-'use strict';
-
-var _interopRequireWildcard = function (obj) { return obj && obj.__esModule ? obj : { 'default': obj }; };
-
-var _expect = require('chai');
-
-var _M = require('../index.js');
-
-var _M2 = _interopRequireWildcard(_M);
-
-describe('Basic math operators', function () {
-  it('should work for add +', function () {
-    _expect.expect(_M2['default'].solve('2+2')).to.equal(4);
-  });
-
-  it('should work for minus -', function () {
-    _expect.expect(_M2['default'].solve('15-3')).to.equal(12);
-  });
-
-  it('should work for divison /', function () {
-    _expect.expect(_M2['default'].solve('20/2')).to.equal(10);
-  });
-
-  it('should work for multiplication *', function () {
-    _expect.expect(_M2['default'].solve('6*3')).to.equal(18);
-  });
-
-  it('should work for power ^', function () {
-    _expect.expect(_M2['default'].solve('5^2')).to.equal(25);
-  });
-
-  it('should work for multi-digit numbers', function () {
-    _expect.expect(_M2['default'].solve('12+15')).to.equal(27);
-  });
-});
-
-describe('Precedence', function () {
-  it('Test case 1', function () {
-    _expect.expect(_M2['default'].solve('2+(2+1)*(1+1)^2')).to.equal(14);
-  });
-
-  it('Test case 2', function () {
-    _expect.expect(_M2['default'].solve('2+5*4/2-2')).to.equal(10);
-  });
-
-  it('Test case 3', function () {
-    _expect.expect(_M2['default'].solve('2+(5*4/2)-2')).to.equal(10);
-  });
-
-  it('Test case 4', function () {
-    _expect.expect(_M2['default'].solve('(2+2)^2+(5+1)*4+(2+(4/2)/2)')).to.equal(16 + 24 + 3);
-  });
-});
-
-describe('Functions', function () {
-  it('should work for with parantheses', function () {
-    _expect.expect(_M2['default'].solve('lg(4) * 5')).to.equal(10);
-  });
-
-  it('should work for without parantheses', function () {
-    _expect.expect(_M2['default'].solve('lg4 * 5')).to.equal(10);
-  });
-});
-
-describe('Constats', function () {
-  it('should work for constant values', function () {
-    _expect.expect(_M2['default'].solve('sin(PI/2)')).to.equal(1);
-  });
-
-  it('should work for functions as constants', function () {
-    _expect.expect(_M2['default'].solve('RAND')).to.not.equal(_M2['default'].solve('RAND'));
-  });
-});

dist/tests/solve.js

@@ -34,6 +34,20 @@ describe('Basic math operators', function () {
   });
 });
 
+describe('Negative Numbers', function () {
+  it('should work for negative numbers after operators', function () {
+    _expect.expect(_M2['default'].solve('2 + -5')).to.equal(-3);
+  });
+
+  it('should work for negative numbers after groups', function () {
+    _expect.expect(_M2['default'].solve('1 + (2 - 5) - 2')).to.equal(-4);
+  });
+
+  it('should work for expressions starting with negative numbers', function () {
+    _expect.expect(_M2['default'].solve('-2 + 1')).to.equal(-1);
+  });
+});
+
 describe('Precedence', function () {
   it('Test case 1', function () {
     _expect.expect(_M2['default'].solve('2+(2+1)*(1+1)^2')).to.equal(14);

equation.js

@@ -331,10 +331,12 @@ var parseExpression = function parseExpression(expression) {
 
   // Create an array of separated numbers & operators
   while (stream.next()) {
-    var cur = stream.current();
+    var cur = stream.current(),
+        past = stack.length - 1;
     if (cur === ' ') {
       continue;
     }
+
     // it's probably a function with a length more than one
     if (!_.isNumber(cur) && !_operators2['default'][cur] && cur !== '.') {
       record += cur;
@@ -344,6 +346,19 @@ var parseExpression = function parseExpression(expression) {
     } else if (_.isNumber(stack[stack.length - 1]) && (_.isNumber(cur) || cur === '.')) {
 
       stack[stack.length - 1] += cur;
+    } else if (stack[past] === '-') {
+      var beforeSign = stack[stack.length - 2];
+
+      if (_operators2['default'][beforeSign]) {
+        stack[past] += cur;
+      } else if (beforeSign === ')') {
+        stack[past] = '+';
+        stack.push('-' + cur);
+      } else if (_.isNumber(beforeSign)) {
+        stack.push(cur);
+      } else {
+        stack[past] += cur;
+      }
     } else {
       stack.push(cur);
     }

lib/index.js

@@ -118,10 +118,12 @@ const parseExpression = expression => {
 
   // Create an array of separated numbers & operators
   while (stream.next()) {
-    const cur = stream.current();
+    const cur = stream.current(),
+          past = stack.length - 1;
     if (cur === ' ') {
       continue;
     }
+
     // it's probably a function with a length more than one
     if (!_.isNumber(cur) && !operators[cur] && cur !== '.') {
       record += cur;
@@ -132,6 +134,19 @@ const parseExpression = expression => {
               (_.isNumber(cur) || cur === '.')) {
 
       stack[stack.length - 1] += cur;
+    } else if (stack[past] === '-') {
+      const beforeSign = stack[stack.length - 2];
+
+      if (operators[beforeSign]) {
+        stack[past] += cur;
+      } else if (beforeSign === ')') {
+        stack[past] = '+';
+        stack.push(`-${cur}`);
+      } else if (_.isNumber(beforeSign)) {
+        stack.push(cur);
+      } else {
+        stack[past] += cur;
+      }
     } else {
       stack.push(cur);
     }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "equations",
-  "version": "1.0.1",
+  "version": "1.1.0",
   "description": "",
   "main": "dist/index.js",
   "directories": {

tests/solve.js

@@ -27,6 +27,20 @@ describe('Basic math operators', () => {
   });
 });
 
+describe('Negative Numbers', () => {
+  it('should work for negative numbers after operators', () => {
+    expect(M.solve('2 + -5')).to.equal(-3);
+  });
+
+  it('should work for negative numbers after groups', () => {
+    expect(M.solve('1 + (2 - 5) - 2')).to.equal(-4);
+  });
+
+  it('should work for expressions starting with negative numbers', () => {
+    expect(M.solve('-2 + 1')).to.equal(-1);
+  });
+});
+
 describe('Precedence', () => {
   it('Test case 1', () => {
     expect(M.solve('2+(2+1)*(1+1)^2')).to.equal(14);