jdk8-mips64-public/nashorn: samples/fixed

     1 /*

     2  * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.

     3  *

     4  * Redistribution and use in source and binary forms, with or without

     5  * modification, are permitted provided that the following conditions

     6  * are met:

     7  *

     8  *   - Redistributions of source code must retain the above copyright

     9  *     notice, this list of conditions and the following disclaimer.

    10  *

    11  *   - Redistributions in binary form must reproduce the above copyright

    12  *     notice, this list of conditions and the following disclaimer in the

    13  *     documentation and/or other materials provided with the distribution.

    14  *

    15  *   - Neither the name of Oracle nor the names of its

    16  *     contributors may be used to endorse or promote products derived

    17  *     from this software without specific prior written permission.

    18  *

    19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS

    20  * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

    21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

    22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR

    23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

    24  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

    25  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

    26  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

    27  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

    28  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

    29  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    30  */

    32 // Simple sample demonstrating "fixed point" computation with Streams

    34 // See also https://mitpress.mit.edu/sicp/chapter1/node21.html#secprocgeneralmethods

    35 var Stream = Java.type("java.util.stream.Stream");

    37 // generic fixed point procedure

    38 function fixed_point(f, init_guess) {

    39   var tolerance = 0.00001;

    40   function close_enough(v1, v2) Math.abs(v1 - v2) < tolerance;

    42   var prev;

    43   return Stream.iterate(init_guess, f)

    44       .filter(function(x) {

    45           try {

    46               return prev == undefined? false : close_enough(prev, x);

    47           } finally {

    48               prev = x;

    49           }

    50       })

    51       .findFirst()

    52       .get();

    53 }

    55 // solution to x = cos(x)

    56 print(fixed_point(Math.cos, 1.0))

    58 // solution to x = sin(x) + cos(x)

    59 print(fixed_point(function(x) Math.sin(x) + Math.cos(x), 1.0));

    61 // square root by Newton's method

    62 // http://en.wikipedia.org/wiki/Newton's_method

    63 function sqrt(n)

    64   fixed_point(function(x) (x + n/x) / 2, 2.0);

    66 print(sqrt(2))

    67 print(sqrt(3))

samples/fixed_point.js@d0fba38a0705