Mega Code Archive
Get the next machine representable number after a number, moving in the direction of another number
<![CDATA[
import java.io.File;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*
*
*/
public class Main {
/**
* Get the next machine representable number after a number, moving
* in the direction of another number.
* <p>
* If <code>direction</code> is greater than or equal to<code>d</code>,
* the smallest machine representable number strictly greater than
* <code>d</code> is returned; otherwise the largest representable number
* strictly less than <code>d</code> is returned.</p>
* <p>
* If <code>d</code> is NaN or Infinite, it is returned unchanged.</p>
*
* @param d base number
* @param direction (the only important thing is whether
* direction is greater or smaller than d)
* @return the next machine representable number in the specified direction
* @since 1.2
*/
public static double nextAfter(double d, double direction) {
// handling of some important special cases
if (Double.isNaN(d) || Double.isInfinite(d)) {
return d;
} else if (d == 0) {
return (direction < 0) ? -Double.MIN_VALUE : Double.MIN_VALUE;
}
// special cases MAX_VALUE to infinity and MIN_VALUE to 0
// are handled just as normal numbers
// split the double in raw components
long bits = Double.doubleToLongBits(d);
long sign = bits & 0x8000000000000000L;
long exponent = bits & 0x7ff0000000000000L;
long mantissa = bits & 0x000fffffffffffffL;
if (d * (direction - d) >= 0) {
// we should increase the mantissa
if (mantissa == 0x000fffffffffffffL) {
return Double.longBitsToDouble(sign |
(exponent + 0x0010000000000000L));
} else {
return Double.longBitsToDouble(sign |
exponent | (mantissa + 1));
}
} else {
// we should decrease the mantissa
if (mantissa == 0L) {
return Double.longBitsToDouble(sign |
(exponent - 0x0010000000000000L) |
0x000fffffffffffffL);
} else {
return Double.longBitsToDouble(sign |
exponent | (mantissa - 1));
}
}
}
}
]]>