michael@0: // Copyright 2009 the Sputnik authors.  All rights reserved.
michael@0: // This code is governed by the BSD license found in the LICENSE file.
michael@0: 
michael@0: /**
michael@0:  * Closures are admitted
michael@0:  *
michael@0:  * @path ch13/13.2/S13.2.1_A5_T2.js
michael@0:  * @description Returning a function that approximates the derivative of f
michael@0:  * using an interval of dx, which should be appropriately small
michael@0:  */
michael@0: 
michael@0: // Return a function that approximates the derivative of f
michael@0: // using an interval of dx, which should be appropriately small.
michael@0: function derivative(f, dx) {
michael@0:     return function(x) {
michael@0:       return (f(x + dx) - f(x)) / dx;
michael@0:     };
michael@0: }
michael@0: 
michael@0: //////////////////////////////////////////////////////////////////////////////
michael@0: //CHECK#1
michael@0: if (Math.abs(derivative(Math.sin, 0.0001)(0) - derivative(Math.sin, 0.0001)(2*Math.PI)) >= 1/65536.0) {
michael@0: 	$ERROR('#1: Math.abs(derivative(Math.sin, 0.0001)(0) - derivative(Math.sin, 0.0001)(2*Math.PI)) <= 1/65536.0');
michael@0: }
michael@0: //
michael@0: //////////////////////////////////////////////////////////////////////////////
michael@0: