Java example source code file (package-info.java)
The package-info.java Java example source code
/* * 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. */ /** * * Decimal floating point library for Java * * <p>Another floating point class. This one is built using radix 10000 * which is 10<sup>4, so its almost decimal. * * <p>The design goals here are: * <ol> * <li>Decimal math, or close to it * <li>Settable precision (but no mix between numbers using different settings) * <li>Portability. Code should be keep as portable as possible. * <li>Performance * <li>Accuracy - Results should always be +/- 1 ULP for basic * algebraic operation</li> * <li>Comply with IEEE 854-1987 as much as possible. * (See IEEE 854-1987 notes below)</li> * </ol> * * <p>Trade offs: * <ol> * <li>Memory foot print. I'm using more memory than necessary to * represent numbers to get better performance.</li> * <li>Digits are bigger, so rounding is a greater loss. So, if you * really need 12 decimal digits, better use 4 base 10000 digits * there can be one partially filled.</li> * </ol> * * <p>Numbers are represented in the following form: * <pre> * n = sign × mant × (radix)<sup>exp; * </pre> * where sign is ±1, mantissa represents a fractional number between * zero and one. mant is the least significant digit. * exp is in the range of -32767 to 32768</p> * * <p>IEEE 854-1987 Notes and differences * * <p>IEEE 854 requires the radix to be either 2 or 10. The radix here is * 10000, so that requirement is not met, but it is possible that a * subclassed can be made to make it behave as a radix 10 * number. It is my opinion that if it looks and behaves as a radix * 10 number then it is one and that requirement would be met.</p> * * <p>The radix of 10000 was chosen because it should be faster to operate * on 4 decimal digits at once instead of one at a time. Radix 10 behavior * can be realized by add an additional rounding step to ensure that * the number of decimal digits represented is constant.</p> * * <p>The IEEE standard specifically leaves out internal data encoding, * so it is reasonable to conclude that such a subclass of this radix * 10000 system is merely an encoding of a radix 10 system.</p> * * <p>IEEE 854 also specifies the existence of "sub-normal" numbers. This * class does not contain any such entities. The most significant radix * 10000 digit is always non-zero. Instead, we support "gradual underflow" * by raising the underflow flag for numbers less with exponent less than * expMin, but don't flush to zero until the exponent reaches MIN_EXP-digits. * Thus the smallest number we can represent would be: * 1E(-(MIN_EXP-digits-1)∗4), eg, for digits=5, MIN_EXP=-32767, that would * be 1e-131092.</p> * * <p>IEEE 854 defines that the implied radix point lies just to the right * of the most significant digit and to the left of the remaining digits. * This implementation puts the implied radix point to the left of all * digits including the most significant one. The most significant digit * here is the one just to the right of the radix point. This is a fine * detail and is really only a matter of definition. Any side effects of * this can be rendered invisible by a subclass.</p> * */ package org.apache.commons.math3.dfp;
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