jdk8-mips64-public/nashorn: samples/fixed_point.js@5ac73294cf68 (annotated)

samples/fixed_point.js@5ac73294cf68 (annotated)

samples/fixed_point.js

Mon, 18 Mar 2019 09:12:13 +0100

author: clanger
date: Mon, 18 Mar 2019 09:12:13 +0100
changeset 2476: 5ac73294cf68
parent 1524: 3f4320a01539
permissions: -rw-r--r--

Merge

 /*
  * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  *   - Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  *
  *   - Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
  *     documentation and/or other materials provided with the distribution.
  *
  *   - Neither the name of Oracle nor the names of its
  *     contributors may be used to endorse or promote products derived
  *     from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 // Simple sample demonstrating "fixed point" computation with Streams
 // See also https://mitpress.mit.edu/sicp/chapter1/node21.html#secprocgeneralmethods
 var Stream = Java.type("java.util.stream.Stream");
 // generic fixed point procedure
 function fixed_point(f, init_guess) {
   var tolerance = 0.00001;
   function close_enough(v1, v2) Math.abs(v1 - v2) < tolerance;
   var prev;
   return Stream.iterate(init_guess, f)
       .filter(function(x) {
           try {
               return prev == undefined? false : close_enough(prev, x);
           } finally {
               prev = x;
           }
       })
       .findFirst()
       .get();
 }
 // solution to x = cos(x)
 print(fixed_point(Math.cos, 1.0))
 // solution to x = sin(x) + cos(x)
 print(fixed_point(function(x) Math.sin(x) + Math.cos(x), 1.0));
 // square root by Newton's method
 // http://en.wikipedia.org/wiki/Newton's_method
 function sqrt(n)
   fixed_point(function(x) (x + n/x) / 2, 2.0);
 print(sqrt(2))
 print(sqrt(3))