"use strict"; Object.defineProperty(exports, "__esModule", { value: true }); exports.createDerivative = void 0; var _is = require("../../utils/is.js"); var _factory = require("../../utils/factory.js"); var name = 'derivative'; var dependencies = ['typed', 'config', 'parse', 'simplify', 'equal', 'isZero', 'numeric', 'ConstantNode', 'FunctionNode', 'OperatorNode', 'ParenthesisNode', 'SymbolNode']; var createDerivative = /* #__PURE__ */(0, _factory.factory)(name, dependencies, function (_ref) { var typed = _ref.typed, config = _ref.config, parse = _ref.parse, simplify = _ref.simplify, equal = _ref.equal, isZero = _ref.isZero, numeric = _ref.numeric, ConstantNode = _ref.ConstantNode, FunctionNode = _ref.FunctionNode, OperatorNode = _ref.OperatorNode, ParenthesisNode = _ref.ParenthesisNode, SymbolNode = _ref.SymbolNode; /** * Takes the derivative of an expression expressed in parser Nodes. * The derivative will be taken over the supplied variable in the * second parameter. If there are multiple variables in the expression, * it will return a partial derivative. * * This uses rules of differentiation which can be found here: * * - [Differentiation rules (Wikipedia)](https://en.wikipedia.org/wiki/Differentiation_rules) * * Syntax: * * derivative(expr, variable) * derivative(expr, variable, options) * * Examples: * * math.derivative('x^2', 'x') // Node {2 * x} * math.derivative('x^2', 'x', {simplify: false}) // Node {2 * 1 * x ^ (2 - 1) * math.derivative('sin(2x)', 'x')) // Node {2 * cos(2 * x)} * math.derivative('2*x', 'x').evaluate() // number 2 * math.derivative('x^2', 'x').evaluate({x: 4}) // number 8 * const f = math.parse('x^2') * const x = math.parse('x') * math.derivative(f, x) // Node {2 * x} * * See also: * * simplify, parse, evaluate * * @param {Node | string} expr The expression to differentiate * @param {SymbolNode | string} variable The variable over which to differentiate * @param {{simplify: boolean}} [options] * There is one option available, `simplify`, which * is true by default. When false, output will not * be simplified. * @return {ConstantNode | SymbolNode | ParenthesisNode | FunctionNode | OperatorNode} The derivative of `expr` */ var derivative = typed('derivative', { 'Node, SymbolNode, Object': function NodeSymbolNodeObject(expr, variable, options) { var constNodes = {}; constTag(constNodes, expr, variable.name); var res = _derivative(expr, constNodes); return options.simplify ? simplify(res) : res; }, 'Node, SymbolNode': function NodeSymbolNode(expr, variable) { return this(expr, variable, { simplify: true }); }, 'string, SymbolNode': function stringSymbolNode(expr, variable) { return this(parse(expr), variable); }, 'string, SymbolNode, Object': function stringSymbolNodeObject(expr, variable, options) { return this(parse(expr), variable, options); }, 'string, string': function stringString(expr, variable) { return this(parse(expr), parse(variable)); }, 'string, string, Object': function stringStringObject(expr, variable, options) { return this(parse(expr), parse(variable), options); }, 'Node, string': function NodeString(expr, variable) { return this(expr, parse(variable)); }, 'Node, string, Object': function NodeStringObject(expr, variable, options) { return this(expr, parse(variable), options); } // TODO: replace the 8 signatures above with 4 as soon as typed-function supports optional arguments /* TODO: implement and test syntax with order of derivatives -> implement as an option {order: number} 'Node, SymbolNode, ConstantNode': function (expr, variable, {order}) { let res = expr for (let i = 0; i < order; i++) { let constNodes = {} constTag(constNodes, expr, variable.name) res = _derivative(res, constNodes) } return res } */ }); derivative._simplify = true; derivative.toTex = function (deriv) { return _derivTex.apply(null, deriv.args); }; // FIXME: move the toTex method of derivative to latex.js. Difficulty is that it relies on parse. // NOTE: the optional "order" parameter here is currently unused var _derivTex = typed('_derivTex', { 'Node, SymbolNode': function NodeSymbolNode(expr, x) { if ((0, _is.isConstantNode)(expr) && (0, _is.typeOf)(expr.value) === 'string') { return _derivTex(parse(expr.value).toString(), x.toString(), 1); } else { return _derivTex(expr.toString(), x.toString(), 1); } }, 'Node, ConstantNode': function NodeConstantNode(expr, x) { if ((0, _is.typeOf)(x.value) === 'string') { return _derivTex(expr, parse(x.value)); } else { throw new Error("The second parameter to 'derivative' is a non-string constant"); } }, 'Node, SymbolNode, ConstantNode': function NodeSymbolNodeConstantNode(expr, x, order) { return _derivTex(expr.toString(), x.name, order.value); }, 'string, string, number': function stringStringNumber(expr, x, order) { var d; if (order === 1) { d = '{d\\over d' + x + '}'; } else { d = '{d^{' + order + '}\\over d' + x + '^{' + order + '}}'; } return d + "\\left[".concat(expr, "\\right]"); } }); /** * Does a depth-first search on the expression tree to identify what Nodes * are constants (e.g. 2 + 2), and stores the ones that are constants in * constNodes. Classification is done as follows: * * 1. ConstantNodes are constants. * 2. If there exists a SymbolNode, of which we are differentiating over, * in the subtree it is not constant. * * @param {Object} constNodes Holds the nodes that are constant * @param {ConstantNode | SymbolNode | ParenthesisNode | FunctionNode | OperatorNode} node * @param {string} varName Variable that we are differentiating * @return {boolean} if node is constant */ // TODO: can we rewrite constTag into a pure function? var constTag = typed('constTag', { 'Object, ConstantNode, string': function ObjectConstantNodeString(constNodes, node) { constNodes[node] = true; return true; }, 'Object, SymbolNode, string': function ObjectSymbolNodeString(constNodes, node, varName) { // Treat other variables like constants. For reasoning, see: // https://en.wikipedia.org/wiki/Partial_derivative if (node.name !== varName) { constNodes[node] = true; return true; } return false; }, 'Object, ParenthesisNode, string': function ObjectParenthesisNodeString(constNodes, node, varName) { return constTag(constNodes, node.content, varName); }, 'Object, FunctionAssignmentNode, string': function ObjectFunctionAssignmentNodeString(constNodes, node, varName) { if (node.params.indexOf(varName) === -1) { constNodes[node] = true; return true; } return constTag(constNodes, node.expr, varName); }, 'Object, FunctionNode | OperatorNode, string': function ObjectFunctionNodeOperatorNodeString(constNodes, node, varName) { if (node.args.length > 0) { var isConst = constTag(constNodes, node.args[0], varName); for (var i = 1; i < node.args.length; ++i) { isConst = constTag(constNodes, node.args[i], varName) && isConst; } if (isConst) { constNodes[node] = true; return true; } } return false; } }); /** * Applies differentiation rules. * * @param {ConstantNode | SymbolNode | ParenthesisNode | FunctionNode | OperatorNode} node * @param {Object} constNodes Holds the nodes that are constant * @return {ConstantNode | SymbolNode | ParenthesisNode | FunctionNode | OperatorNode} The derivative of `expr` */ var _derivative = typed('_derivative', { 'ConstantNode, Object': function ConstantNodeObject(node) { return createConstantNode(0); }, 'SymbolNode, Object': function SymbolNodeObject(node, constNodes) { if (constNodes[node] !== undefined) { return createConstantNode(0); } return createConstantNode(1); }, 'ParenthesisNode, Object': function ParenthesisNodeObject(node, constNodes) { return new ParenthesisNode(_derivative(node.content, constNodes)); }, 'FunctionAssignmentNode, Object': function FunctionAssignmentNodeObject(node, constNodes) { if (constNodes[node] !== undefined) { return createConstantNode(0); } return _derivative(node.expr, constNodes); }, 'FunctionNode, Object': function FunctionNodeObject(node, constNodes) { if (node.args.length !== 1) { funcArgsCheck(node); } if (constNodes[node] !== undefined) { return createConstantNode(0); } var arg0 = node.args[0]; var arg1; var div = false; // is output a fraction? var negative = false; // is output negative? var funcDerivative; switch (node.name) { case 'cbrt': // d/dx(cbrt(x)) = 1 / (3x^(2/3)) div = true; funcDerivative = new OperatorNode('*', 'multiply', [createConstantNode(3), new OperatorNode('^', 'pow', [arg0, new OperatorNode('/', 'divide', [createConstantNode(2), createConstantNode(3)])])]); break; case 'sqrt': case 'nthRoot': // d/dx(sqrt(x)) = 1 / (2*sqrt(x)) if (node.args.length === 1) { div = true; funcDerivative = new OperatorNode('*', 'multiply', [createConstantNode(2), new FunctionNode('sqrt', [arg0])]); } else if (node.args.length === 2) { // Rearrange from nthRoot(x, a) -> x^(1/a) arg1 = new OperatorNode('/', 'divide', [createConstantNode(1), node.args[1]]); // Is a variable? constNodes[arg1] = constNodes[node.args[1]]; return _derivative(new OperatorNode('^', 'pow', [arg0, arg1]), constNodes); } break; case 'log10': arg1 = createConstantNode(10); /* fall through! */ case 'log': if (!arg1 && node.args.length === 1) { // d/dx(log(x)) = 1 / x funcDerivative = arg0.clone(); div = true; } else if (node.args.length === 1 && arg1 || node.args.length === 2 && constNodes[node.args[1]] !== undefined) { // d/dx(log(x, c)) = 1 / (x*ln(c)) funcDerivative = new OperatorNode('*', 'multiply', [arg0.clone(), new FunctionNode('log', [arg1 || node.args[1]])]); div = true; } else if (node.args.length === 2) { // d/dx(log(f(x), g(x))) = d/dx(log(f(x)) / log(g(x))) return _derivative(new OperatorNode('/', 'divide', [new FunctionNode('log', [arg0]), new FunctionNode('log', [node.args[1]])]), constNodes); } break; case 'pow': constNodes[arg1] = constNodes[node.args[1]]; // Pass to pow operator node parser return _derivative(new OperatorNode('^', 'pow', [arg0, node.args[1]]), constNodes); case 'exp': // d/dx(e^x) = e^x funcDerivative = new FunctionNode('exp', [arg0.clone()]); break; case 'sin': // d/dx(sin(x)) = cos(x) funcDerivative = new FunctionNode('cos', [arg0.clone()]); break; case 'cos': // d/dx(cos(x)) = -sin(x) funcDerivative = new OperatorNode('-', 'unaryMinus', [new FunctionNode('sin', [arg0.clone()])]); break; case 'tan': // d/dx(tan(x)) = sec(x)^2 funcDerivative = new OperatorNode('^', 'pow', [new FunctionNode('sec', [arg0.clone()]), createConstantNode(2)]); break; case 'sec': // d/dx(sec(x)) = sec(x)tan(x) funcDerivative = new OperatorNode('*', 'multiply', [node, new FunctionNode('tan', [arg0.clone()])]); break; case 'csc': // d/dx(csc(x)) = -csc(x)cot(x) negative = true; funcDerivative = new OperatorNode('*', 'multiply', [node, new FunctionNode('cot', [arg0.clone()])]); break; case 'cot': // d/dx(cot(x)) = -csc(x)^2 negative = true; funcDerivative = new OperatorNode('^', 'pow', [new FunctionNode('csc', [arg0.clone()]), createConstantNode(2)]); break; case 'asin': // d/dx(asin(x)) = 1 / sqrt(1 - x^2) div = true; funcDerivative = new FunctionNode('sqrt', [new OperatorNode('-', 'subtract', [createConstantNode(1), new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)])])]); break; case 'acos': // d/dx(acos(x)) = -1 / sqrt(1 - x^2) div = true; negative = true; funcDerivative = new FunctionNode('sqrt', [new OperatorNode('-', 'subtract', [createConstantNode(1), new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)])])]); break; case 'atan': // d/dx(atan(x)) = 1 / (x^2 + 1) div = true; funcDerivative = new OperatorNode('+', 'add', [new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)]), createConstantNode(1)]); break; case 'asec': // d/dx(asec(x)) = 1 / (|x|*sqrt(x^2 - 1)) div = true; funcDerivative = new OperatorNode('*', 'multiply', [new FunctionNode('abs', [arg0.clone()]), new FunctionNode('sqrt', [new OperatorNode('-', 'subtract', [new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)]), createConstantNode(1)])])]); break; case 'acsc': // d/dx(acsc(x)) = -1 / (|x|*sqrt(x^2 - 1)) div = true; negative = true; funcDerivative = new OperatorNode('*', 'multiply', [new FunctionNode('abs', [arg0.clone()]), new FunctionNode('sqrt', [new OperatorNode('-', 'subtract', [new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)]), createConstantNode(1)])])]); break; case 'acot': // d/dx(acot(x)) = -1 / (x^2 + 1) div = true; negative = true; funcDerivative = new OperatorNode('+', 'add', [new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)]), createConstantNode(1)]); break; case 'sinh': // d/dx(sinh(x)) = cosh(x) funcDerivative = new FunctionNode('cosh', [arg0.clone()]); break; case 'cosh': // d/dx(cosh(x)) = sinh(x) funcDerivative = new FunctionNode('sinh', [arg0.clone()]); break; case 'tanh': // d/dx(tanh(x)) = sech(x)^2 funcDerivative = new OperatorNode('^', 'pow', [new FunctionNode('sech', [arg0.clone()]), createConstantNode(2)]); break; case 'sech': // d/dx(sech(x)) = -sech(x)tanh(x) negative = true; funcDerivative = new OperatorNode('*', 'multiply', [node, new FunctionNode('tanh', [arg0.clone()])]); break; case 'csch': // d/dx(csch(x)) = -csch(x)coth(x) negative = true; funcDerivative = new OperatorNode('*', 'multiply', [node, new FunctionNode('coth', [arg0.clone()])]); break; case 'coth': // d/dx(coth(x)) = -csch(x)^2 negative = true; funcDerivative = new OperatorNode('^', 'pow', [new FunctionNode('csch', [arg0.clone()]), createConstantNode(2)]); break; case 'asinh': // d/dx(asinh(x)) = 1 / sqrt(x^2 + 1) div = true; funcDerivative = new FunctionNode('sqrt', [new OperatorNode('+', 'add', [new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)]), createConstantNode(1)])]); break; case 'acosh': // d/dx(acosh(x)) = 1 / sqrt(x^2 - 1); XXX potentially only for x >= 1 (the real spectrum) div = true; funcDerivative = new FunctionNode('sqrt', [new OperatorNode('-', 'subtract', [new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)]), createConstantNode(1)])]); break; case 'atanh': // d/dx(atanh(x)) = 1 / (1 - x^2) div = true; funcDerivative = new OperatorNode('-', 'subtract', [createConstantNode(1), new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)])]); break; case 'asech': // d/dx(asech(x)) = -1 / (x*sqrt(1 - x^2)) div = true; negative = true; funcDerivative = new OperatorNode('*', 'multiply', [arg0.clone(), new FunctionNode('sqrt', [new OperatorNode('-', 'subtract', [createConstantNode(1), new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)])])])]); break; case 'acsch': // d/dx(acsch(x)) = -1 / (|x|*sqrt(x^2 + 1)) div = true; negative = true; funcDerivative = new OperatorNode('*', 'multiply', [new FunctionNode('abs', [arg0.clone()]), new FunctionNode('sqrt', [new OperatorNode('+', 'add', [new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)]), createConstantNode(1)])])]); break; case 'acoth': // d/dx(acoth(x)) = -1 / (1 - x^2) div = true; negative = true; funcDerivative = new OperatorNode('-', 'subtract', [createConstantNode(1), new OperatorNode('^', 'pow', [arg0.clone(), createConstantNode(2)])]); break; case 'abs': // d/dx(abs(x)) = abs(x)/x funcDerivative = new OperatorNode('/', 'divide', [new FunctionNode(new SymbolNode('abs'), [arg0.clone()]), arg0.clone()]); break; case 'gamma': // Needs digamma function, d/dx(gamma(x)) = gamma(x)digamma(x) default: throw new Error('Function "' + node.name + '" is not supported by derivative, or a wrong number of arguments is passed'); } var op, func; if (div) { op = '/'; func = 'divide'; } else { op = '*'; func = 'multiply'; } /* Apply chain rule to all functions: F(x) = f(g(x)) F'(x) = g'(x)*f'(g(x)) */ var chainDerivative = _derivative(arg0, constNodes); if (negative) { chainDerivative = new OperatorNode('-', 'unaryMinus', [chainDerivative]); } return new OperatorNode(op, func, [chainDerivative, funcDerivative]); }, 'OperatorNode, Object': function OperatorNodeObject(node, constNodes) { if (constNodes[node] !== undefined) { return createConstantNode(0); } if (node.op === '+') { // d/dx(sum(f(x)) = sum(f'(x)) return new OperatorNode(node.op, node.fn, node.args.map(function (arg) { return _derivative(arg, constNodes); })); } if (node.op === '-') { // d/dx(+/-f(x)) = +/-f'(x) if (node.isUnary()) { return new OperatorNode(node.op, node.fn, [_derivative(node.args[0], constNodes)]); } // Linearity of differentiation, d/dx(f(x) +/- g(x)) = f'(x) +/- g'(x) if (node.isBinary()) { return new OperatorNode(node.op, node.fn, [_derivative(node.args[0], constNodes), _derivative(node.args[1], constNodes)]); } } if (node.op === '*') { // d/dx(c*f(x)) = c*f'(x) var constantTerms = node.args.filter(function (arg) { return constNodes[arg] !== undefined; }); if (constantTerms.length > 0) { var nonConstantTerms = node.args.filter(function (arg) { return constNodes[arg] === undefined; }); var nonConstantNode = nonConstantTerms.length === 1 ? nonConstantTerms[0] : new OperatorNode('*', 'multiply', nonConstantTerms); var newArgs = constantTerms.concat(_derivative(nonConstantNode, constNodes)); return new OperatorNode('*', 'multiply', newArgs); } // Product Rule, d/dx(f(x)*g(x)) = f'(x)*g(x) + f(x)*g'(x) return new OperatorNode('+', 'add', node.args.map(function (argOuter) { return new OperatorNode('*', 'multiply', node.args.map(function (argInner) { return argInner === argOuter ? _derivative(argInner, constNodes) : argInner.clone(); })); })); } if (node.op === '/' && node.isBinary()) { var arg0 = node.args[0]; var arg1 = node.args[1]; // d/dx(f(x) / c) = f'(x) / c if (constNodes[arg1] !== undefined) { return new OperatorNode('/', 'divide', [_derivative(arg0, constNodes), arg1]); } // Reciprocal Rule, d/dx(c / f(x)) = -c(f'(x)/f(x)^2) if (constNodes[arg0] !== undefined) { return new OperatorNode('*', 'multiply', [new OperatorNode('-', 'unaryMinus', [arg0]), new OperatorNode('/', 'divide', [_derivative(arg1, constNodes), new OperatorNode('^', 'pow', [arg1.clone(), createConstantNode(2)])])]); } // Quotient rule, d/dx(f(x) / g(x)) = (f'(x)g(x) - f(x)g'(x)) / g(x)^2 return new OperatorNode('/', 'divide', [new OperatorNode('-', 'subtract', [new OperatorNode('*', 'multiply', [_derivative(arg0, constNodes), arg1.clone()]), new OperatorNode('*', 'multiply', [arg0.clone(), _derivative(arg1, constNodes)])]), new OperatorNode('^', 'pow', [arg1.clone(), createConstantNode(2)])]); } if (node.op === '^' && node.isBinary()) { var _arg = node.args[0]; var _arg2 = node.args[1]; if (constNodes[_arg] !== undefined) { // If is secretly constant; 0^f(x) = 1 (in JS), 1^f(x) = 1 if ((0, _is.isConstantNode)(_arg) && (isZero(_arg.value) || equal(_arg.value, 1))) { return createConstantNode(0); } // d/dx(c^f(x)) = c^f(x)*ln(c)*f'(x) return new OperatorNode('*', 'multiply', [node, new OperatorNode('*', 'multiply', [new FunctionNode('log', [_arg.clone()]), _derivative(_arg2.clone(), constNodes)])]); } if (constNodes[_arg2] !== undefined) { if ((0, _is.isConstantNode)(_arg2)) { // If is secretly constant; f(x)^0 = 1 -> d/dx(1) = 0 if (isZero(_arg2.value)) { return createConstantNode(0); } // Ignore exponent; f(x)^1 = f(x) if (equal(_arg2.value, 1)) { return _derivative(_arg, constNodes); } } // Elementary Power Rule, d/dx(f(x)^c) = c*f'(x)*f(x)^(c-1) var powMinusOne = new OperatorNode('^', 'pow', [_arg.clone(), new OperatorNode('-', 'subtract', [_arg2, createConstantNode(1)])]); return new OperatorNode('*', 'multiply', [_arg2.clone(), new OperatorNode('*', 'multiply', [_derivative(_arg, constNodes), powMinusOne])]); } // Functional Power Rule, d/dx(f^g) = f^g*[f'*(g/f) + g'ln(f)] return new OperatorNode('*', 'multiply', [new OperatorNode('^', 'pow', [_arg.clone(), _arg2.clone()]), new OperatorNode('+', 'add', [new OperatorNode('*', 'multiply', [_derivative(_arg, constNodes), new OperatorNode('/', 'divide', [_arg2.clone(), _arg.clone()])]), new OperatorNode('*', 'multiply', [_derivative(_arg2, constNodes), new FunctionNode('log', [_arg.clone()])])])]); } throw new Error('Operator "' + node.op + '" is not supported by derivative, or a wrong number of arguments is passed'); } }); /** * Ensures the number of arguments for a function are correct, * and will throw an error otherwise. * * @param {FunctionNode} node */ function funcArgsCheck(node) { // TODO add min, max etc if ((node.name === 'log' || node.name === 'nthRoot' || node.name === 'pow') && node.args.length === 2) { return; } // There should be an incorrect number of arguments if we reach here // Change all args to constants to avoid unidentified // symbol error when compiling function for (var i = 0; i < node.args.length; ++i) { node.args[i] = createConstantNode(0); } node.compile().evaluate(); throw new Error('Expected TypeError, but none found'); } /** * Helper function to create a constant node with a specific type * (number, BigNumber, Fraction) * @param {number} value * @param {string} [valueType] * @return {ConstantNode} */ function createConstantNode(value, valueType) { return new ConstantNode(numeric(value, valueType || config.number)); } return derivative; }); exports.createDerivative = createDerivative;