// test OperatorNode
var assert = require('assert');
var approx = require('../../../tools/approx');
var math = require('../../../index');
var Node = math.expression.node.Node;
var ConstantNode = math.expression.node.ConstantNode;
var SymbolNode = math.expression.node.SymbolNode;
var OperatorNode = math.expression.node.OperatorNode;
var ConditionalNode = math.expression.node.ConditionalNode;

describe('OperatorNode', function() {

  it ('should create an OperatorNode', function () {
    var n = new OperatorNode('op', 'fn', []);
    assert(n instanceof OperatorNode);
    assert(n instanceof Node);
    assert.equal(n.type, 'OperatorNode');
  });

  it ('should have isOperatorNode', function () {
    var node = new OperatorNode('op', 'fn', []);
    assert(node.isOperatorNode);
  });

  it ('should throw an error when calling without new operator', function () {
    var a = new ConstantNode(2);
    var b = new ConstantNode(3);
    assert.throws(function () {OperatorNode('+', 'add', [a, b])}, SyntaxError);
  });

  it ('should compile an OperatorNode', function () {
    var a = new ConstantNode(2);
    var b = new ConstantNode(3);
    var n = new OperatorNode('+', 'add', [a, b]);

    var expr = n.compile();

    assert.equal(expr.eval(), 5);
  });

  it ('should throw an error in case of unresolved operator function', function () {
    var a = new ConstantNode(2);
    var b = new ConstantNode(3);
    var n = new OperatorNode('***', 'foo', [a, b]);

    assert.throws(function () {
      n.compile();
    }, /Function foo missing in provided namespace/);
  });

  it ('should filter an OperatorNode', function () {
    var a = new ConstantNode(2);
    var b = new ConstantNode(3);
    var n = new OperatorNode('+', 'add', [a, b]);

    assert.deepEqual(n.filter(function (node) {return node instanceof OperatorNode}),  [n]);
    assert.deepEqual(n.filter(function (node) {return node instanceof SymbolNode}),    []);
    assert.deepEqual(n.filter(function (node) {return node instanceof ConstantNode}),  [a, b]);
    assert.deepEqual(n.filter(function (node) {return node instanceof ConstantNode && node.value == '2'}),  [a]);
    assert.deepEqual(n.filter(function (node) {return node instanceof ConstantNode && node.value == '4'}),  []);
  });

  it ('should filter an OperatorNode without contents', function () {
    var n = new OperatorNode('op', 'fn', []);

    assert.deepEqual(n.filter(function (node) {return node instanceof OperatorNode}),  [n]);
    assert.deepEqual(n.filter(function (node) {return node instanceof SymbolNode}),    []);
  });

  it ('should run forEach on an OperatorNode', function () {
    // x^2-x
    var a = new SymbolNode('x');
    var b = new ConstantNode(2);
    var c = new OperatorNode('^', 'pow', [a, b]);
    var d = new SymbolNode('x');
    var e = new OperatorNode('-', 'subtract', [c, d]);

    var nodes = [];
    var paths = [];
    e.forEach(function (node, path, parent) {
      nodes.push(node);
      paths.push(path);
      assert.strictEqual(parent, e);
    });

    assert.equal(nodes.length, 2);
    assert.strictEqual(nodes[0], c);
    assert.strictEqual(nodes[1], d);
    assert.deepEqual(paths, ['args[0]', 'args[1]']);
  });

  it ('should map an OperatorNode', function () {
    // x^2-x
    var a = new SymbolNode('x');
    var b = new ConstantNode(2);
    var c = new OperatorNode('^', 'pow', [a, b]);
    var d = new SymbolNode('x');
    var e = new OperatorNode('-', 'subtract', [c, d]);

    var nodes = [];
    var paths = [];
    var f = new ConstantNode(3);
    var g = e.map(function (node, path, parent) {
      nodes.push(node);
      paths.push(path);
      assert.strictEqual(parent, e);

      return node instanceof SymbolNode && node.name == 'x' ? f : node;
    });

    assert.equal(nodes.length, 2);
    assert.strictEqual(nodes[0], c);
    assert.strictEqual(nodes[1], d);
    assert.deepEqual(paths, ['args[0]', 'args[1]']);

    assert.notStrictEqual(g,  e);
    assert.strictEqual(g.args[0], e.args[0]);
    assert.strictEqual(g.args[0].args[0], a); // nested x is not replaced
    assert.deepEqual(g.args[0].args[1], b);
    assert.deepEqual(g.args[1],  f);
  });

  it('should map an implicit OperatorNode', function () {
    var x = new SymbolNode('x');
    var y = new SymbolNode('y');
    var product = new OperatorNode('*', 'multiply', [x, y], true /* implicit */);

    assert.deepEqual(product.map(function(x) { return x; }), product);
  });

  it ('should throw an error when the map callback does not return a node', function () {
    var a = new SymbolNode('x');
    var b = new ConstantNode(2);
    var c = new OperatorNode('^', 'pow', [a, b]);

    assert.throws(function () {
      c.map(function () {});
    }, /Callback function must return a Node/)
  });

  it ('should transform an OperatorNodes parameters', function () {
    // x^2-x
    var a = new SymbolNode('x');
    var b = new ConstantNode(2);
    var c = new OperatorNode('^', 'pow', [a, b]);
    var d = new SymbolNode('x');
    var e = new OperatorNode('-', 'subtract', [c, d]);

    var f = new ConstantNode(3);
    var g = e.transform(function (node) {
      return node instanceof SymbolNode && node.name == 'x' ? f : node;
    });

    assert.deepEqual(g.args[1],  f);
  });

  it ('should transform an OperatorNode itself', function () {
    // x^2-x
    var a = new SymbolNode('x');
    var b = new ConstantNode(2);
    var c = new OperatorNode('+', 'add', [a, b]);

    var f = new ConstantNode(3);
    var g = c.transform(function (node) {
      return node instanceof OperatorNode ? f : node;
    });

    assert.notStrictEqual(g, c);
    assert.deepEqual(g,  f);
  });

  it ('should clone an OperatorNode', function () {
    // x^2-x
    var a = new SymbolNode('x');
    var b = new ConstantNode(2);
    var c = new OperatorNode('+', 'add', [a, b]);

    var d = c.clone();
    assert(d instanceof OperatorNode);
    assert.deepEqual(d, c);
    assert.notStrictEqual(d, c);
    assert.notStrictEqual(d.args, c.args);
    assert.strictEqual(d.args[0], c.args[0]);
    assert.strictEqual(d.args[1], c.args[1]);
  });

  it ('should clone implicit multiplications', function () {
    var two = new ConstantNode(2);
    var x = new SymbolNode('x');
    var node = new OperatorNode('*', 'multiply', [two, x], true);

    assert.equal('2 x', node.toString());
    assert.strictEqual(true, node.clone().implicit);
    assert.equal(node.toString(), node.clone().toString());
  });

  it ('test equality another Node', function () {
    var a = new OperatorNode('+', 'add', [new SymbolNode('x'), new ConstantNode(2)]);
    var b = new OperatorNode('+', 'add', [new SymbolNode('x'), new ConstantNode(2)]);
    var c = new OperatorNode('*', 'multiply', [new SymbolNode('x'), new ConstantNode(2)]);
    var d = new OperatorNode('*', 'add', [new SymbolNode('x'), new ConstantNode(3)]);
    var e = new OperatorNode('*', 'add', [new SymbolNode('x'), new ConstantNode(2), new ConstantNode(4)]);

    assert.strictEqual(a.equals(null), false);
    assert.strictEqual(a.equals(undefined), false);
    assert.strictEqual(a.equals(b), true);
    assert.strictEqual(a.equals(c), false);
    assert.strictEqual(a.equals(d), false);
    assert.strictEqual(a.equals(e), false);
  });

  describe('toString', function () {
    it ('should stringify an OperatorNode', function () {
      var a = new ConstantNode(2);
      var b = new ConstantNode(3);
      var c = new ConstantNode(4);

      var n = new OperatorNode('+', 'add', [a, b]);
      assert.equal(n.toString(), '2 + 3');
    });

    it ('should stringify an OperatorNode with factorial', function () {
      var a = new ConstantNode(2);
      var n = new OperatorNode('!', 'factorial', [a]);
      assert.equal(n.toString(), '2!');
    });

    it ('should stringify an OperatorNode with unary minus', function () {
      var a = new ConstantNode(2);
      var n = new OperatorNode('-', 'unaryMinus', [a]);
      assert.equal(n.toString(), '-2');
    });

    it ('should stringify an OperatorNode with zero arguments', function () {
      var n = new OperatorNode('foo', 'foo', []);
      assert.equal(n.toString(), 'foo()');
    });

    it ('should stringify an OperatorNode with more than two operators', function () {
      var a = new ConstantNode(2);
      var b = new ConstantNode(3);
      var c = new ConstantNode(4);

      var n = new OperatorNode('foo', 'foo', [a, b, c]);
      assert.equal(n.toString(), 'foo(2, 3, 4)');

    });

    it ('should stringify addition and multiplication with more than two operands', function () {
      var a = new SymbolNode('a');
      var b = new SymbolNode('b');
      var c = new SymbolNode('c');

      var add = new OperatorNode('+', 'add', [a, b, c]);
      var multiply = new OperatorNode('*', 'multiply', [a, b, c]);
      var implicitMultiply = new OperatorNode('*', 'multiply', [a, b, c], true);

      assert.equal(add.toString(), 'a + b + c');
      assert.equal(multiply.toString(), 'a * b * c');
      assert.equal(implicitMultiply.toString(), 'a b c');
    });

    it ('should stringify addition and multiplication with more than two operands including OperatorNode', function () {
      var a = new SymbolNode('a');
      var b = new SymbolNode('b');
      var c = new SymbolNode('c');
      var d = new SymbolNode('d');

      var mult = new OperatorNode('*', 'multiply', [a,b]);
      var add = new OperatorNode('+', 'add', [a, b]);

      var multipleMultWithMult = new OperatorNode('*', 'multiply', [c, mult, d]);
      var multipleMultWithAdd = new OperatorNode('*', 'multiply', [c, add, d]);
      var multipleAddWithMult = new OperatorNode('+', 'add', [c, mult, d]);
      var multipleAddWithAdd = new OperatorNode('+', 'add', [c, add, d]);

      assert.equal(multipleMultWithMult.toString(), 'c * a * b * d');
      assert.equal(multipleMultWithAdd.toString(), 'c * (a + b) * d');
      assert.equal(multipleAddWithMult.toString(), 'c + a * b + d');
      assert.equal(multipleAddWithAdd.toString(), 'c + a + b + d');
    });

    it ('should stringify an OperatorNode that contains an operatornode with more than two operands', function () {
      var a = new SymbolNode('a');
      var b = new SymbolNode('b');
      var c = new SymbolNode('c');
      var d = new SymbolNode('d');

      var mult = new OperatorNode('*', 'multiply', [a, b, c]);
      var add = new OperatorNode('+', 'add', [a, b, c]);

      var addWithMult = new OperatorNode('+', 'add', [mult, d]);
      var addWithAdd = new OperatorNode('+', 'add', [add, d]);
      var multWithMult = new OperatorNode('*', 'multiply', [mult, d]);
      var multWithAdd = new OperatorNode('*', 'multiply', [add, d]);

      assert.equal(addWithMult.toString(), 'a * b * c + d');
      assert.equal(addWithAdd.toString(), 'a + b + c + d');
      assert.equal(multWithMult.toString(), 'a * b * c * d');
      assert.equal(multWithAdd.toString(), '(a + b + c) * d');

    });

    it ('should stringify an OperatorNode with nested operator nodes', function () {
      var a = new ConstantNode(2);
      var b = new ConstantNode(3);
      var c = new ConstantNode(4);
      var d = new ConstantNode(5);

      var n1 = new OperatorNode('+', 'add', [a, b]);
      var n2 = new OperatorNode('-', 'subtract', [c, d]);
      var n3 = new OperatorNode('*', 'multiply', [n1, n2]);

      assert.equal(n1.toString(), '2 + 3');
      assert.equal(n2.toString(), '4 - 5');
      assert.equal(n3.toString(), '(2 + 3) * (4 - 5)');
    });

    it ('should stringify left associative OperatorNodes that are associative with another Node', function () {
      assert.equal(math.parse('(a+b)+c').toString({parenthesis: 'auto'}), 'a + b + c');
      assert.equal(math.parse('a+(b+c)').toString({parenthesis: 'auto'}), 'a + b + c');
      assert.equal(math.parse('(a+b)-c').toString({parenthesis: 'auto'}), 'a + b - c');
      assert.equal(math.parse('a+(b-c)').toString({parenthesis: 'auto'}), 'a + b - c');

      assert.equal(math.parse('(a*b)*c').toString({parenthesis: 'auto'}), 'a * b * c');
      assert.equal(math.parse('a*(b*c)').toString({parenthesis: 'auto'}), 'a * b * c');
      assert.equal(math.parse('(a*b)/c').toString({parenthesis: 'auto'}), 'a * b / c');
      assert.equal(math.parse('a*(b/c)').toString({parenthesis: 'auto'}), 'a * b / c');
    });

    it ('should stringify left associative OperatorNodes that are not associative with another Node', function () {
      assert.equal(math.parse('(a-b)-c').toString({parenthesis: 'auto'}), 'a - b - c');
      assert.equal(math.parse('a-(b-c)').toString({parenthesis: 'auto'}), 'a - (b - c)');
      assert.equal(math.parse('(a-b)+c').toString({parenthesis: 'auto'}), 'a - b + c');
      assert.equal(math.parse('a-(b+c)').toString({parenthesis: 'auto'}), 'a - (b + c)');

      assert.equal(math.parse('(a/b)/c').toString({parenthesis: 'auto'}), 'a / b / c');
      assert.equal(math.parse('a/(b/c)').toString({parenthesis: 'auto'}), 'a / (b / c)');
      assert.equal(math.parse('(a/b)*c').toString({parenthesis: 'auto'}), 'a / b * c');
      assert.equal(math.parse('a/(b*c)').toString({parenthesis: 'auto'}), 'a / (b * c)');
    });

    it ('should stringify right associative OperatorNodes that are not associative with another Node', function () {
      assert.equal(math.parse('(a^b)^c').toString({parenthesis: 'auto'}), '(a ^ b) ^ c');
      assert.equal(math.parse('a^(b^c)').toString({parenthesis: 'auto'}), 'a ^ b ^ c');
    });

    it ('should stringify unary OperatorNodes containing a binary OperatorNode', function () {
      assert.equal(math.parse('(a*b)!').toString(), '(a * b)!');
      assert.equal(math.parse('-(a*b)').toString(), '-(a * b)');
      assert.equal(math.parse('-(a+b)').toString(), '-(a + b)');
    });

    it ('should stringify unary OperatorNodes containing a unary OperatorNode', function () {
      assert.equal(math.parse('(-a)!').toString({parenthesis: 'auto'}), '(-a)!');
      assert.equal(math.parse('-(a!)').toString({parenthesis: 'auto'}), '-a!');
      assert.equal(math.parse('-(-a)').toString({parenthesis: 'auto'}), '-(-a)');
    });
  });

  it ('should stringify an OperatorNode with custom toString', function () {
    //Also checks if the custom functions get passed on to the children
    var customFunction = function (node, options) {
      if (node.type === 'OperatorNode') {
        return node.op + node.fn + '(' 
          + node.args[0].toString(options)
          + ', ' +  node.args[1].toString(options) + ')';
      }
      else if (node.type === 'ConstantNode') {
        return 'const(' + node.value + ', ' + node.valueType + ')'
      }
    };

    var a = new ConstantNode(1);
    var b = new ConstantNode(2);

    var n1 = new OperatorNode('+', 'add', [a, b]);
    var n2 = new OperatorNode('-', 'subtract', [a, b]);

    assert.equal(n1.toString({handler: customFunction}), '+add(const(1, number), const(2, number))');
    assert.equal(n2.toString({handler: customFunction}), '-subtract(const(1, number), const(2, number))');
  });

  it ('should stringify an OperatorNode with custom toString for a single operator', function () {
    //Also checks if the custom functions get passed on to the children
    var customFunction = function (node, options) {
      if ((node.type === 'OperatorNode') && (node.fn === 'add')) {
        return node.args[0].toString(options)
          + node.op + node.fn + node.op + 
          node.args[1].toString(options);
      }
      else if (node.type === 'ConstantNode') {
        return 'const(' + node.value + ', ' + node.valueType + ')'
      }
    };

    var a = new ConstantNode(1);
    var b = new ConstantNode(2);

    var n = new OperatorNode('+', 'add', [a, b]);

    assert.equal(n.toString({handler: customFunction}), 'const(1, number)+add+const(2, number)');
  });

  it ('should respect the \'all\' parenthesis option', function () {
    assert.equal(math.parse('1+1+1').toString({parenthesis: 'all'}), '(1 + 1) + 1' );
    assert.equal(math.parse('1+1+1').toTex({parenthesis: 'all'}), '\\left(1+1\\right)+1' );
  });

  it ('should correctly LaTeX fractions in \'all\' parenthesis mode', function () {
    assert.equal(math.parse('1/2/3').toTex({parenthesis: 'all'}), '\\frac{\\left(\\frac{1}{2}\\right)}{3}');
  });

  it ('should LaTeX an OperatorNode', function () {
    var a = new ConstantNode(2);
    var b = new ConstantNode(3);
    var c = new ConstantNode(4);

    var n = new OperatorNode('+', 'add', [a, b]);
    assert.equal(n.toTex(), '2+3');
  });

  it ('should LaTeX an OperatorNode with factorial', function () {
    var a = new ConstantNode(2);
    var n = new OperatorNode('!', 'factorial', [a]);
    assert.equal(n.toTex(), '2!');
  });

  it ('should LaTeX an OperatorNode with factorial of an OperatorNode', function () {
    var a = new ConstantNode(2);
    var b = new ConstantNode(3);

    var sub = new OperatorNode('-', 'subtract', [a, b]);
    var add = new OperatorNode('+', 'add', [a, b]);
    var mult = new OperatorNode('*', 'multiply', [a, b]);
    var div = new OperatorNode('/', 'divide', [a, b]);

    var n1= new OperatorNode('!', 'factorial', [sub] );
    var n2= new OperatorNode('!', 'factorial', [add] );
    var n3= new OperatorNode('!', 'factorial', [mult] );
    var n4= new OperatorNode('!', 'factorial', [div] );
    assert.equal(n1.toTex(), '\\left(2-3\\right)!');
    assert.equal(n2.toTex(), '\\left(2+3\\right)!');
    assert.equal(n3.toTex(), '\\left(2\\cdot3\\right)!');
    assert.equal(n4.toTex(), '\\frac{2}{3}!');
  });

  it ('should LaTeX an OperatorNode with unary minus', function () {
    var a = new ConstantNode(2);
    var b = new ConstantNode(3);

    var sub = new OperatorNode('-', 'subtract', [a, b]);
    var add = new OperatorNode('+', 'add', [a, b]);

    var n1 = new OperatorNode('-', 'unaryMinus', [a]);
    var n2 = new OperatorNode('-', 'unaryMinus', [sub]);
    var n3 = new OperatorNode('-', 'unaryMinus', [add]);

    assert.equal(n1.toTex(), '-2');
    assert.equal(n2.toTex(), '-\\left(2-3\\right)');
    assert.equal(n3.toTex(), '-\\left(2+3\\right)');
  });

  it ('should LaTeX an OperatorNode that subtracts an OperatorNode', function() {
    var a = new ConstantNode(1);
    var b = new ConstantNode(2);
    var c = new ConstantNode(3);

    var sub = new OperatorNode('-', 'subtract', [b, c]);
    var add = new OperatorNode('+', 'add', [b, c]);

    var n1 = new OperatorNode('-', 'subtract', [a, sub]);
    var n2 = new OperatorNode('-', 'subtract', [a, add]);

    assert.equal(n1.toTex(), '1-\\left(2-3\\right)');
    assert.equal(n2.toTex(), '1-\\left(2+3\\right)');
  });

  it ('should LaTeX an OperatorNode with zero arguments', function () {
    var n = new OperatorNode('foo', 'foo', []);
    assert.equal(n.toTex(), '\\mathrm{foo}\\left(\\right)');
  });

  it ('should LaTeX an OperatorNode with more than two operators', function () {
    var a = new ConstantNode(2);
    var b = new ConstantNode(3);
    var c = new ConstantNode(4);

    var n = new OperatorNode('foo', 'foo', [a, b, c]);
    assert.equal(n.toTex(), '\\mathrm{foo}\\left(2,3,4\\right)');

  });

  it ('should LaTeX an OperatorNode with nested operator nodes', function () {
    var a = new ConstantNode(2);
    var b = new ConstantNode(3);
    var c = new ConstantNode(4);
    var d = new ConstantNode(5);

    var n1 = new OperatorNode('+', 'add', [a, b]);
    var n2 = new OperatorNode('-', 'subtract', [c, d]);
    var n3 = new OperatorNode('*', 'multiply', [n1, n2]);

    var m2 = new OperatorNode('*', 'multiply', [n1, c]);
    var m3 = new OperatorNode('-', 'subtract', [m2, d]);

    assert.equal(n1.toTex(), '2+3');
    assert.equal(n2.toTex(), '4-5');
    assert.equal(n3.toTex(), '\\left(2+3\\right)\\cdot\\left(4-5\\right)');
    assert.equal(m3.toTex(), '\\left(2+3\\right)\\cdot4-5');
  });

  it ('should LaTeX addition and multiplication with more than two operands', function () {
    var a = new SymbolNode('a');
    var b = new SymbolNode('b');
    var c = new SymbolNode('c');

    var add = new OperatorNode('+', 'add', [a, b, c]);
    var multiply = new OperatorNode('*', 'multiply', [a, b, c]);
    var implicitMultiply = new OperatorNode('*', 'multiply', [a, b, c], true);

    assert.equal(add.toTex(), ' a+\\mathrm{b}+ c');
    assert.equal(multiply.toTex(), ' a\\cdot\\mathrm{b}\\cdot c');
    assert.equal(implicitMultiply.toTex(), ' a~\\mathrm{b}~ c');
  });

  it ('should LaTeX addition and multiplication with more than two operands including OperatorNode', function () {
    var a = new SymbolNode('a');
    var b = new SymbolNode('b');
    var c = new SymbolNode('c');
    var d = new SymbolNode('d');

    var mult = new OperatorNode('*', 'multiply', [a,b]);
    var add = new OperatorNode('+', 'add', [a, b]);

    var multipleMultWithMult = new OperatorNode('*', 'multiply', [c, mult, d]);
    var multipleMultWithAdd = new OperatorNode('*', 'multiply', [c, add, d]);
    var multipleAddWithMult = new OperatorNode('+', 'add', [c, mult, d]);
    var multipleAddWithAdd = new OperatorNode('+', 'add', [c, add, d]);

    assert.equal(multipleMultWithMult.toTex(), ' c\\cdot a\\cdot\\mathrm{b}\\cdot d');
    assert.equal(multipleMultWithAdd.toTex(), ' c\\cdot\\left( a+\\mathrm{b}\\right)\\cdot d');
    assert.equal(multipleAddWithMult.toTex(), ' c+ a\\cdot\\mathrm{b}+ d');
    assert.equal(multipleAddWithAdd.toTex(), ' c+ a+\\mathrm{b}+ d');
  });

  it ('should LaTeX an OperatorNode that contains an operatornode with more than two operands', function () {
    var a = new SymbolNode('a');
    var b = new SymbolNode('b');
    var c = new SymbolNode('c');
    var d = new SymbolNode('d');

    var mult = new OperatorNode('*', 'multiply', [a, b, c]);
    var add = new OperatorNode('+', 'add', [a, b, c]);

    var addWithMult = new OperatorNode('+', 'add', [mult, d]);
    var addWithAdd = new OperatorNode('+', 'add', [add, d]);
    var multWithMult = new OperatorNode('*', 'multiply', [mult, d]);
    var multWithAdd = new OperatorNode('*', 'multiply', [add, d]);

    assert.equal(addWithMult.toTex(), ' a\\cdot\\mathrm{b}\\cdot c+ d');
    assert.equal(addWithAdd.toTex(), ' a+\\mathrm{b}+ c+ d');
    assert.equal(multWithMult.toTex(), ' a\\cdot\\mathrm{b}\\cdot c\\cdot d');
    assert.equal(multWithAdd.toTex(), '\\left( a+\\mathrm{b}+ c\\right)\\cdot d');
  });

  it('should LaTeX fractions with operators that are enclosed in parenthesis', function () {
    var a = new ConstantNode(1);
    var b = new ConstantNode(2);

    var add = new OperatorNode('+', 'add', [a,a]);
    var frac = new OperatorNode('/', 'divide', [add,b]);
    assert.equal(frac.toTex(), '\\frac{1+1}{2}');
  });

  it ('should have an identifier', function () {
    var a = new ConstantNode(1);
    var b = new ConstantNode(2);

    var n = new OperatorNode('+', 'add', [a, b]);

    assert.equal(n.getIdentifier(), 'OperatorNode:add');
  });

  it ('should LaTeX an OperatorNode with custom toTex', function () {
    //Also checks if the custom functions get passed on to the children
    var customFunction = function (node, options) {
      if (node.type === 'OperatorNode') {
        return node.op + node.fn + '(' 
          + node.args[0].toTex(options)
          + ', ' +  node.args[1].toTex(options) + ')';
      }
      else if (node.type === 'ConstantNode') {
        return 'const\\left(' + node.value + ', ' + node.valueType + '\\right)'
      }
    };

    var a = new ConstantNode(1);
    var b = new ConstantNode(2);

    var n1 = new OperatorNode('+', 'add', [a, b]);
    var n2 = new OperatorNode('-', 'subtract', [a, b]);

    assert.equal(n1.toTex({handler: customFunction}), '+add(const\\left(1, number\\right), const\\left(2, number\\right))');
    assert.equal(n2.toTex({handler: customFunction}), '-subtract(const\\left(1, number\\right), const\\left(2, number\\right))');
  });

  it ('should LaTeX an OperatorNode with custom toTex for a single operator', function () {
    //Also checks if the custom functions get passed on to the children
    var customFunction = function (node, options) {
      if ((node.type === 'OperatorNode') && (node.fn === 'add')) {
        return node.args[0].toTex(options)
          + node.op + node.fn + node.op + 
          node.args[1].toTex(options);
      }
      else if (node.type === 'ConstantNode') {
        return 'const\\left(' + node.value + ', ' + node.valueType + '\\right)'
      }
    };

    var a = new ConstantNode(1);
    var b = new ConstantNode(2);

    var n = new OperatorNode('+', 'add', [a, b]);

    assert.equal(n.toTex({handler: customFunction}), 'const\\left(1, number\\right)+add+const\\left(2, number\\right)');
  });

  it ('should LaTeX powers of fractions with parentheses', function () {
    var a = new ConstantNode(1);
    var frac = new OperatorNode('/', 'divide', [a,a]);
    var pow = new OperatorNode('^', 'pow', [frac, a]);

    assert.equal(pow.toTex(), '\\left({\\frac{1}{1}}\\right)^{1}');
  });

  it ('should LaTeX powers of conditions with parentheses', function () {
    var a = new ConstantNode(1);
    var cond = new ConditionalNode(a, a, a);
    var pow = new OperatorNode('^', 'pow', [cond, a]);

    assert.equal(pow.toTex(), '\\left({\\begin{cases} {1}, &\\quad{\\text{if }\\;1}\\\\{1}, &\\quad{\\text{otherwise}}\\end{cases}}\\right)^{1}');
  });

  it ('should LaTeX simple expressions in \'auto\' mode', function () {
    //this covers a bug that was triggered previously
    assert.equal(math.parse('1+(1+1)').toTex({parenthesis: 'auto'}), '1+1+1');
  });

  it ('should stringify implicit multiplications', function () {
    var a = math.parse('4a');
    var b = math.parse('4 a');
    var c = math.parse('a b');
    var d = math.parse('2a b');
    var e = math.parse('a b c');
    var f = math.parse('(2+3)a');
    var g = math.parse('(2+3)2');
    var h = math.parse('2(3+4)');

    assert.equal(a.toString(), a.toString({implicit: 'hide'}));
    assert.equal(a.toString({implicit: 'hide'}), '4 a');
    assert.equal(a.toString({implicit: 'show'}), '4 * a');

    assert.equal(b.toString(), b.toString({implicit: 'hide'}));
    assert.equal(b.toString({implicit: 'hide'}), '4 a');
    assert.equal(b.toString({implicit: 'show'}), '4 * a');

    assert.equal(c.toString(), c.toString({implicit: 'hide'}));
    assert.equal(c.toString({implicit: 'hide'}), 'a b');
    assert.equal(c.toString({implicit: 'show'}), 'a * b');

    assert.equal(d.toString(), d.toString({implicit: 'hide'}));
    assert.equal(d.toString({implicit: 'hide'}), '2 a b');
    assert.equal(d.toString({implicit: 'show'}), '2 * a * b');

    assert.equal(e.toString(), e.toString({implicit: 'hide'}));
    assert.equal(e.toString({implicit: 'hide'}), 'a b c');
    assert.equal(e.toString({implicit: 'show'}), 'a * b * c');

    assert.equal(f.toString(), f.toString({implicit: 'hide'}));
    assert.equal(f.toString({implicit: 'hide'}), '(2 + 3) a');
    assert.equal(f.toString({implicit: 'show'}), '(2 + 3) * a');

    assert.equal(g.toString(), g.toString({implicit: 'hide'}));
    assert.equal(g.toString({implicit: 'hide'}), '(2 + 3) 2');
    assert.equal(g.toString({implicit: 'show'}), '(2 + 3) * 2');

    assert.equal(h.toString(), h.toString({implicit: 'hide'}));
    assert.equal(h.toString({implicit: 'hide'}), '2 (3 + 4)');
    assert.equal(h.toString({implicit: 'show'}), '2 * (3 + 4)');
  });

  it ('should LaTeX implicit multiplications', function () {
    var a = math.parse('4a');
    var b = math.parse('4 a');
    var c = math.parse('a b');
    var d = math.parse('2a b');
    var e = math.parse('a b c');
    var f = math.parse('(2+3)a');
    var g = math.parse('(2+3)2');
    var h = math.parse('2(3+4)');

    assert.equal(a.toTex(), a.toTex({implicit: 'hide'}));
    assert.equal(a.toTex({implicit: 'hide'}), '4~ a');
    assert.equal(a.toTex({implicit: 'show'}), '4\\cdot a');

    assert.equal(b.toTex(), b.toTex({implicit: 'hide'}));
    assert.equal(b.toTex({implicit: 'hide'}), '4~ a');
    assert.equal(b.toTex({implicit: 'show'}), '4\\cdot a');

    assert.equal(c.toTex(), c.toTex({implicit: 'hide'}));
    assert.equal(c.toTex({implicit: 'hide'}), ' a~\\mathrm{b}');
    assert.equal(c.toTex({implicit: 'show'}), ' a\\cdot\\mathrm{b}');

    assert.equal(d.toTex(), d.toTex({implicit: 'hide'}));
    assert.equal(d.toTex({implicit: 'hide'}), '2~ a~\\mathrm{b}');
    assert.equal(d.toTex({implicit: 'show'}), '2\\cdot a\\cdot\\mathrm{b}');

    assert.equal(e.toTex(), e.toTex({implicit: 'hide'}));
    assert.equal(e.toTex({implicit: 'hide'}), ' a~\\mathrm{b}~ c');
    assert.equal(e.toTex({implicit: 'show'}), ' a\\cdot\\mathrm{b}\\cdot c');

    assert.equal(f.toTex(), f.toTex({implicit: 'hide'}));
    assert.equal(f.toTex({implicit: 'hide'}), '\\left(2+3\\right)~ a');
    assert.equal(f.toTex({implicit: 'show'}), '\\left(2+3\\right)\\cdot a');

    assert.equal(g.toTex(), g.toTex({implicit: 'hide'}));
    assert.equal(g.toTex({implicit: 'hide'}), '\\left(2+3\\right)~2');
    assert.equal(g.toTex({implicit: 'show'}), '\\left(2+3\\right)\\cdot2');

    assert.equal(h.toTex(), h.toTex({implicit: 'hide'}));
    assert.equal(h.toTex({implicit: 'hide'}), '2~\\left(3+4\\right)');
    assert.equal(h.toTex({implicit: 'show'}), '2\\cdot\\left(3+4\\right)');
  });

  it ('should stringify implicit multiplications between ConstantNodes with parentheses', function () {
    var a = math.parse('(4)(4)(4)(4)');
    var b = math.parse('4b*4(4)');
    var c = math.parse('(4(4(4)))');

    assert.equal(a.toString({implicit: 'hide', parenthesis: 'auto'}), '(4) (4) (4) (4)');
    assert.equal(b.toString({implicit: 'hide', parenthesis: 'auto'}), '4 b * 4 (4)');
    assert.equal(c.toString({implicit: 'hide', parenthesis: 'auto'}), '4 (4 (4))');
  });

  it ('should LaTeX implicit multiplications between ConstantNodes with parentheses', function () {
    var a = math.parse('(4)(4)(4)(4)');
    var b = math.parse('4b*4(4)');
    var c = math.parse('(4(4(4)))');

    assert.equal(a.toTex({implicit: 'hide', parenthesis: 'auto'}), '\\left(4\\right)~\\left(4\\right)~\\left(4\\right)~\\left(4\\right)');
    assert.equal(b.toTex({implicit: 'hide', parenthesis: 'auto'}), '4~\\mathrm{b}\\cdot4~\\left(4\\right)');
    assert.equal(c.toTex({implicit: 'hide', parenthesis: 'auto'}), '4~\\left(4~\\left(4\\right)\\right)');
  });

  it ('should HTML implicit multiplications between ConstantNodes with parentheses', function () {
    var a = math.parse('(4)(4)(4)(4)');
    var b = math.parse('4b*4(4)');
    var c = math.parse('(4(4(4)))');

    assert.equal(a.toHTML({implicit: 'hide', parenthesis: 'auto'}), '<span class="math-parenthesis math-round-parenthesis">(</span><span class="math-number">4</span><span class="math-parenthesis math-round-parenthesis">)</span><span class="math-operator math-binary-operator math-implicit-binary-operator"></span><span class="math-parenthesis math-round-parenthesis">(</span><span class="math-number">4</span><span class="math-parenthesis math-round-parenthesis">)</span><span class="math-operator math-binary-operator math-implicit-binary-operator"></span><span class="math-parenthesis math-round-parenthesis">(</span><span class="math-number">4</span><span class="math-parenthesis math-round-parenthesis">)</span><span class="math-operator math-binary-operator math-implicit-binary-operator"></span><span class="math-parenthesis math-round-parenthesis">(</span><span class="math-number">4</span><span class="math-parenthesis math-round-parenthesis">)</span>');
    assert.equal(b.toHTML({implicit: 'hide', parenthesis: 'auto'}), '<span class="math-number">4</span><span class="math-operator math-binary-operator math-implicit-binary-operator"></span><span class="math-symbol">b</span><span class="math-operator math-binary-operator math-explicit-binary-operator">*</span><span class="math-number">4</span><span class="math-operator math-binary-operator math-implicit-binary-operator"></span><span class="math-parenthesis math-round-parenthesis">(</span><span class="math-number">4</span><span class="math-parenthesis math-round-parenthesis">)</span>');
    assert.equal(c.toHTML({implicit: 'hide', parenthesis: 'auto'}), '<span class="math-number">4</span><span class="math-operator math-binary-operator math-implicit-binary-operator"></span><span class="math-parenthesis math-round-parenthesis">(</span><span class="math-number">4</span><span class="math-operator math-binary-operator math-implicit-binary-operator"></span><span class="math-parenthesis math-round-parenthesis">(</span><span class="math-number">4</span><span class="math-parenthesis math-round-parenthesis">)</span><span class="math-parenthesis math-round-parenthesis">)</span>');
  });
});