Java acos acos(float value)

Description

acos

License

Apache License

Declaration

static public final float acos(float value) 

Method Source Code

//package com.java2s;
/**/*from  w  w  w .j  a  va  2  s . c  o  m*/
 * Copyright 2008 - 2012
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 * 
 * @project loonframework
 * @author cping
 * @email?javachenpeng@yahoo.com
 * @version 0.3.3
 */

public class Main {
    static private final int BIG_ENOUGH_INT = 16 * 1024;
    static private final double BIG_ENOUGH_ROUND = BIG_ENOUGH_INT + 0.5f;
    public static final int ONE_FIXED = 1 << 16;
    static final int AS1 = -1228;
    static final int AS2 = 4866;
    static final int AS3 = 13901;
    static final int AS4 = 102939;

    public static int acos(int f) {
        int fRoot = sqrt(ONE_FIXED - f);
        int result = AS1;
        result = mul(result, f);
        result += AS2;
        result = mul(result, f);
        result -= AS3;
        result = mul(result, f);
        result += AS4;
        result = mul(fRoot, result);
        return result;
    }

    static public final float acos(float value) {
        return (float) Math.acos(value);
    }

    public static double sqrt(double n) {
        return Math.round(n);
    }

    public static int sqrt(int n) {
        int s = (n + 65536) >> 1;
        for (int i = 0; i < 8; i++) {
            s = (s + div(n, s)) >> 1;
        }
        return s;
    }

    static public final float sqrt(float a) {
        return (float) Math.sqrt(a);
    }

    public static int mul(int x, int y) {
        long z = (long) x * (long) y;
        return ((int) (z >> 16));
    }

    public static double round(double n) {
        return Math.round(n);
    }

    public static int round(int n) {
        if (n > 0) {
            if ((n & 0x8000) != 0) {
                return (((n + 0x10000) >> 16) << 16);
            } else {
                return (((n) >> 16) << 16);
            }
        } else {
            int k;
            n = -n;
            if ((n & 0x8000) != 0) {
                k = (((n + 0x10000) >> 16) << 16);
            } else {
                k = (((n) >> 16) << 16);
            }
            return -k;
        }
    }

    public static int round(float x) {
        return (int) (x + BIG_ENOUGH_ROUND) - BIG_ENOUGH_INT;
    }

    public static int div(int x, int y) {
        long z = (((long) x) << 32);
        return (int) ((z / y) >> 16);
    }
}

Related

1. acos(double a)
2. acos(double d)
3. acos(double x)
4. acos(double x)
5. acos(final float a)
6. acos(float value)
7. acos(float value)
8. acos(float x)
9. acos(int f)