classes
MathContext.as
package com.rouche.math
{
/* ------------------------------------------------------------------ */
/* MathContext -- Math context settings */
/* ------------------------------------------------------------------ */
/* Copyright IBM Corporation, 1997, 2000, 2005. All Rights Reserved. */
/* */
/* The MathContext object encapsulates the settings used by the */
/* BigDecimal class; it could also be used by other arithmetics. */
/* ------------------------------------------------------------------ */
/* Notes: */
/* */
/* 1. The properties are checked for validity on construction, so */
/* the BigDecimal class may assume that they are correct. */
/* ------------------------------------------------------------------ */
/* Author: Mike Cowlishaw */
/* 1997.09.03 Initial version (edited from netrexx.lang.RexxSet) */
/* 1997.09.12 Add lostDigits property */
/* 1998.05.02 Make the class immutable and final; drop set methods */
/* 1998.06.05 Add Round (rounding modes) property */
/* 1998.06.25 Rename from DecimalContext; allow digits=0 */
/* 1998.10.12 change to com.ibm.icu.math package */
/* 1999.02.06 add javadoc comments */
/* 1999.03.05 simplify; changes from discussion with J. Bloch */
/* 1999.03.13 1.00 release to IBM Centre for Java Technology */
/* 1999.07.10 1.04 flag serialization unused */
/* 2000.01.01 1.06 copyright update */
/* ------------------------------------------------------------------ */
/**
* The <code>MathContext</code> immutable class encapsulates the
* settings understood by the operator methods of the {@link BigDecimal}
* class (and potentially other classes). Operator methods are those
* that effect an operation on a number or a pair of numbers.
* <p>
* The settings, which are not base-dependent, comprise:
* <ol>
* <li><code>digits</code>:
* the number of digits (precision) to be used for an operation
* <li><code>form</code>:
* the form of any exponent that results from the operation
* <li><code>lostDigits</code>:
* whether checking for lost digits is enabled
* <li><code>roundingMode</code>:
* the algorithm to be used for rounding.
* </ol>
* <p>
* When provided, a <code>MathContext</code> object supplies the
* settings for an operation directly.
* <p>
* When <code>MathContext.DEFAULT</code> is provided for a
* <code>MathContext</code> parameter then the default settings are used
* (<code>9, SCIENTIFIC, false, ROUND_HALF_UP</code>).
* <p>
* In the <code>BigDecimal</code> class, all methods which accept a
* <code>MathContext</code> object defaults) also have a version of the
* method which does not accept a MathContext parameter. These versions
* carry out unlimited precision fixed point arithmetic (as though the
* settings were (<code>0, PLAIN, false, ROUND_HALF_UP</code>).
* <p>
* The instance variables are shared with default access (so they are
* directly accessible to the <code>BigDecimal</code> class), but must
* never be changed.
* <p>
* The rounding mode constants have the same names and values as the
* constants of the same name in <code>java.math.BigDecimal</code>, to
* maintain compatibility with earlier versions of
* <code>BigDecimal</code>.
*
* @see BigDecimal
* @author Mike Cowlishaw
* @stable ICU 2.0
*/
public class MathContext {
/* ----- Properties ----- */
/* properties public constant */
/**
* Plain (fixed point) notation, without any exponent.
* Used as a setting to control the form of the result of a
* <code>BigDecimal</code> operation.
* A zero result in plain form may have a decimal part of one or
* more zeros.
*
* @see #ENGINEERING
* @see #SCIENTIFIC
* @stable ICU 2.0
*/
public static const NOTATION_PLAIN:int = 0; // [no exponent]
/**
* Standard floating point notation (with scientific exponential
* format, where there is one digit before any decimal point).
* Used as a setting to control the form of the result of a
* <code>BigDecimal</code> operation.
* A zero result in plain form may have a decimal part of one or
* more zeros.
*
* @see #ENGINEERING
* @see #PLAIN
* @stable ICU 2.0
*/
public static const NOTATION_SCIENTIFIC:int = 1; // 1 digit before .
/**
* Standard floating point notation (with engineering exponential
* format, where the power of ten is a multiple of 3).
* Used as a setting to control the form of the result of a
* <code>BigDecimal</code> operation.
* A zero result in plain form may have a decimal part of one or
* more zeros.
*
* @see #PLAIN
* @see #SCIENTIFIC
* @stable ICU 2.0
*/
public static const NOTATION_ENGINEERING:int = 2; // 1-3 digits before .
// The rounding modes match the original BigDecimal class values
/**
* Rounding mode to round to a more positive number.
* Used as a setting to control the rounding mode used during a
* <code>BigDecimal</code> operation.
* <p>
* If any of the discarded digits are non-zero then the result
* should be rounded towards the next more positive digit.
* @stable ICU 2.0
*/
public static const ROUND_CEILING:int = 2;
/**
* Rounding mode to round towards zero.
* Used as a setting to control the rounding mode used during a
* <code>BigDecimal</code> operation.
* <p>
* All discarded digits are ignored (truncated). The result is
* neither incremented nor decremented.
* @stable ICU 2.0
*/
public static const ROUND_DOWN:int = 1;
/**
* Rounding mode to round to a more negative number.
* Used as a setting to control the rounding mode used during a
* <code>BigDecimal</code> operation.
* <p>
* If any of the discarded digits are non-zero then the result
* should be rounded towards the next more negative digit.
* @stable ICU 2.0
*/
public static const ROUND_FLOOR:int = 3;
/**
* Rounding mode to round to nearest neighbor, where an equidistant
* value is rounded down.
* Used as a setting to control the rounding mode used during a
* <code>BigDecimal</code> operation.
* <p>
* If the discarded digits represent greater than half (0.5 times)
* the value of a one in the next position then the result should be
* rounded up (away from zero). Otherwise the discarded digits are
* ignored.
* @stable ICU 2.0
*/
public static const ROUND_HALF_DOWN:int = 5;
/**
* Rounding mode to round to nearest neighbor, where an equidistant
* value is rounded to the nearest even neighbor.
* Used as a setting to control the rounding mode used during a
* <code>BigDecimal</code> operation.
* <p>
* If the discarded digits represent greater than half (0.5 times)
* the value of a one in the next position then the result should be
* rounded up (away from zero). If they represent less than half,
* then the result should be rounded down.
* <p>
* Otherwise (they represent exactly half) the result is rounded
* down if its rightmost digit is even, or rounded up if its
* rightmost digit is odd (to make an even digit).
* @stable ICU 2.0
*/
public static const ROUND_HALF_EVEN:int = 6;
/**
* Rounding mode to round to nearest neighbor, where an equidistant
* value is rounded up.
* Used as a setting to control the rounding mode used during a
* <code>BigDecimal</code> operation.
* <p>
* If the discarded digits represent greater than or equal to half
* (0.5 times) the value of a one in the next position then the result
* should be rounded up (away from zero). Otherwise the discarded
* digits are ignored.
* @stable ICU 2.0
*/
public static const ROUND_HALF_UP:int = 4;
/**
* Rounding mode to assert that no rounding is necessary.
* Used as a setting to control the rounding mode used during a
* <code>BigDecimal</code> operation.
* <p>
* Rounding (potential loss of information) is not permitted.
* If any of the discarded digits are non-zero then an
* <code>ArithmeticException</code> should be thrown.
* @stable ICU 2.0
*/
public static const ROUND_UNNECESSARY:int = 7;
/**
* Rounding mode to round away from zero.
* Used as a setting to control the rounding mode used during a
* <code>BigDecimal</code> operation.
* <p>
* If any of the discarded digits are non-zero then the result will
* be rounded up (away from zero).
* @stable ICU 2.0
*/
public static const ROUND_UP:int = 0;
/* properties shared */
/**
* The number of digits (precision) to be used for an operation.
* A value of 0 indicates that unlimited precision (as many digits
* as are required) will be used.
* <p>
* The {@link BigDecimal} operator methods use this value to
* determine the precision of results.
* Note that leading zeros (in the integer part of a number) are
* never significant.
* <p>
* <code>digits</code> will always be non-negative.
*
* @serial
*/
internal var digits:int;
/**
* The form of results from an operation.
* <p>
* The {@link BigDecimal} operator methods use this value to
* determine the form of results, in particular whether and how
* exponential notation should be used.
*
* @see #ENGINEERING
* @see #PLAIN
* @see #SCIENTIFIC
* @serial
*/
internal var form:int; // values for this must fit in a byte
/**
* Controls whether lost digits checking is enabled for an
* operation.
* Set to <code>true</code> to enable checking, or
* to <code>false</code> to disable checking.
* <p>
* When enabled, the {@link BigDecimal} operator methods check
* the precision of their operand or operands, and throw an
* <code>ArithmeticException</code> if an operand is more precise
* than the digits setting (that is, digits would be lost).
* When disabled, operands are rounded to the specified digits.
*
* @serial
*/
internal var lostDigits:Boolean;
/**
* The rounding algorithm to be used for an operation.
* <p>
* The {@link BigDecimal} operator methods use this value to
* determine the algorithm to be used when non-zero digits have to
* be discarded in order to reduce the precision of a result.
* The value must be one of the public constants whose name starts
* with <code>ROUND_</code>.
*
* @see #ROUND_CEILING
* @see #ROUND_DOWN
* @see #ROUND_FLOOR
* @see #ROUND_HALF_DOWN
* @see #ROUND_HALF_EVEN
* @see #ROUND_HALF_UP
* @see #ROUND_UNNECESSARY
* @see #ROUND_UP
* @serial
*/
internal var roundingMode:int;
/* properties private constant */
// default settings
private static const DEFAULT_FORM:int = NOTATION_SCIENTIFIC;
private static const DEFAULT_DIGITS:int = 9;
private static const DEFAULT_LOSTDIGITS:Boolean = false;
private static const DEFAULT_ROUNDINGMODE:int = ROUND_HALF_UP;
/* properties private constant */
private static const MIN_DIGITS:int = 0; // smallest value for DIGITS.
private static const MAX_DIGITS:int = 999999999; // largest value for DIGITS. If increased,
// the BigDecimal class may need update.
// list of valid rounding mode values, most common two first
private static const ROUNDS:Array = [ROUND_HALF_UP,ROUND_UNNECESSARY,ROUND_CEILING,ROUND_DOWN,ROUND_FLOOR,ROUND_HALF_DOWN,ROUND_HALF_EVEN,ROUND_UP];
private static const ROUNDWORDS:Array = ["ROUND_HALF_UP","ROUND_UNNECESSARY","ROUND_CEILING","ROUND_DOWN","ROUND_FLOOR","ROUND_HALF_DOWN","ROUND_HALF_EVEN","ROUND_UP"]; // matching names of the ROUNDS values
/* properties public constant */
/**
* A <code>MathContext</code> object initialized to the default
* settings for general-purpose arithmetic. That is,
* <code>digits=9 form=SCIENTIFIC lostDigits=false
* roundingMode=ROUND_HALF_UP</code>.
*
* @see #SCIENTIFIC
* @see #ROUND_HALF_UP
* @stable ICU 2.0
*/
public static const DEFAULT:MathContext = new MathContext(DEFAULT_DIGITS,DEFAULT_FORM,DEFAULT_LOSTDIGITS,DEFAULT_ROUNDINGMODE);
public static const PLAIN:MathContext = new MathContext(0,NOTATION_PLAIN); // context for plain unlimited math
/* ----- Constructors ----- */
/**
* Constructs a new <code>MathContext</code> with a specified
* precision, form, lostDigits, and roundingMode setting.
*
* An <code>IllegalArgumentException</code> is thrown if the
* <code>setdigits</code> parameter is out of range
* (<0 or >999999999), or if the value given for the
* <code>setform</code> or <code>setroundingmode</code> parameters is
* not one of the appropriate constants.
*
* @param setdigits The <code>int</code> digits setting
* for this <code>MathContext</code>.
* @param setform The <code>int</code> form setting
* for this <code>MathContext</code>.
* @param setlostdigits The <code>boolean</code> lostDigits
* setting for this <code>MathContext</code>.
* @param setroundingmode The <code>int</code> roundingMode setting
* for this <code>MathContext</code>.
* @throws IllegalArgumentException parameter out of range.
* @stable ICU 2.0
*/
public function MathContext(setdigits:int, setform:int = DEFAULT_FORM, setlostdigits:Boolean = DEFAULT_LOSTDIGITS, setroundingmode:int = DEFAULT_ROUNDINGMODE) {
// set values, after checking
if (setdigits!=DEFAULT_DIGITS) {
if (setdigits<MIN_DIGITS) {
throw new Error("Digits too small:"+" "+setdigits);
}
if (setdigits>MAX_DIGITS) {
throw new Error("Digits too large:"+" "+setdigits);
}
}
{/*select*/
if (setform==NOTATION_SCIENTIFIC) {
// [most common]
} else if (setform==NOTATION_ENGINEERING) {
} else if (setform==NOTATION_PLAIN) {
} else {
throw new Error("Bad form value:"+" "+setform);
}
}
if ((!(isValidRound(setroundingmode)))) {
throw new Error("Bad roundingMode value:"+" "+setroundingmode);
}
digits=setdigits;
form=setform;
lostDigits=setlostdigits; // [no bad value possible]
roundingMode=setroundingmode;
}
/**
* Returns the digits setting.
* This value is always non-negative.
*
* @return an <code>int</code> which is the value of the digits
* setting
* @stable ICU 2.0
*/
public function getDigits():int {
return digits;
}
/**
* Returns the form setting.
* This will be one of
* {@link #ENGINEERING},
* {@link #PLAIN}, or
* {@link #SCIENTIFIC}.
*
* @return an <code>int</code> which is the value of the form setting
* @stable ICU 2.0
*/
public function getForm():int {
return form;
}
/**
* Returns the lostDigits setting.
* This will be either <code>true</code> (enabled) or
* <code>false</code> (disabled).
*
* @return a <code>boolean</code> which is the value of the lostDigits
* setting
* @stable ICU 2.0
*/
public function getLostDigits():Boolean {
return lostDigits;
}
/**
* Returns the roundingMode setting.
* This will be one of
* {@link #ROUND_CEILING},
* {@link #ROUND_DOWN},
* {@link #ROUND_FLOOR},
* {@link #ROUND_HALF_DOWN},
* {@link #ROUND_HALF_EVEN},
* {@link #ROUND_HALF_UP},
* {@link #ROUND_UNNECESSARY}, or
* {@link #ROUND_UP}.
*
* @return an <code>int</code> which is the value of the roundingMode
* setting
* @stable ICU 2.0
*/
public function getRoundingMode():int {
return roundingMode;
}
/** Returns the <code>MathContext</code> as a readable string.
* The <code>String</code> returned represents the settings of the
* <code>MathContext</code> object as four blank-delimited words
* separated by a single blank and with no leading or trailing blanks,
* as follows:
* <ol>
* <li>
* <code>digits=</code>, immediately followed by
* the value of the digits setting as a numeric word.
* <li>
* <code>form=</code>, immediately followed by
* the value of the form setting as an uppercase word
* (one of <code>SCIENTIFIC</code>, <code>PLAIN</code>, or
* <code>ENGINEERING</code>).
* <li>
* <code>lostDigits=</code>, immediately followed by
* the value of the lostDigits setting
* (<code>1</code> if enabled, <code>0</code> if disabled).
* <li>
* <code>roundingMode=</code>, immediately followed by
* the value of the roundingMode setting as a word.
* This word will be the same as the name of the corresponding public
* constant.
* </ol>
* <p>
* For example:
* <br><code>
* digits=9 form=SCIENTIFIC lostDigits=0 roundingMode=ROUND_HALF_UP
* </code>
* <p>
* Additional words may be appended to the result of
* <code>toString</code> in the future if more properties are added
* to the class.
*
* @return a <code>String</code> representing the context settings.
* @stable ICU 2.0
*/
public function toString():String {
var formstr:String = null;
var r:int = 0;
var roundword:String = null;
{/*select*/
if (form==NOTATION_SCIENTIFIC) {
formstr="SCIENTIFIC";
} else if (form==NOTATION_ENGINEERING) {
formstr="ENGINEERING";
} else{
formstr="PLAIN";/* form=PLAIN */
}
}
{
var one:int = ROUNDS.length;
r = 0;
for(; one > 0; one--, r++){
if (roundingMode==ROUNDS[r]) {
roundword=ROUNDWORDS[r];
break;
}
}
}/*r*/
return "digits="+digits+" "+"form="+formstr+" "+"lostDigits="+(lostDigits?"1":"0")+" "+"roundingMode="+roundword;
}
/* <sgml> Test whether round is valid. </sgml> */
// This could be made shared for use by BigDecimal for setScale.
private static function isValidRound(testround:int):Boolean {
var r:int = 0;
{
var two:int = ROUNDS.length;
r=0;
for(; two > 0; two--,r++){
if (testround==ROUNDS[r]) {
return true;
}
}
}/*r*/
return false;
}
}
}