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 // © 2016 and later: Unicode, Inc. and others.
 // License & terms of use: http://www.unicode.org/copyright.html
 /*
 ********************************************************************************
 *   Copyright (C) 1997-2016, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 ********************************************************************************
 *
 * File DECIMFMT.H
 *
 * Modification History:
 *
 *   Date        Name        Description
 *   02/19/97    aliu        Converted from java.
 *   03/20/97    clhuang     Updated per C++ implementation.
 *   04/03/97    aliu        Rewrote parsing and formatting completely, and
 *                           cleaned up and debugged.  Actually works now.
 *   04/17/97    aliu        Changed DigitCount to int per code review.
 *   07/10/97    helena      Made ParsePosition a class and get rid of the function
 *                           hiding problems.
 *   09/09/97    aliu        Ported over support for exponential formats.
 *   07/20/98    stephen     Changed documentation
 *   01/30/13    emmons      Added Scaling methods
 ********************************************************************************
 */
 
 #ifndef DECIMFMT_H
 #define DECIMFMT_H
 
 #include "unicode/utypes.h"
 
 #if U_SHOW_CPLUSPLUS_API
 
 /**
  * \file
  * \brief C++ API: Compatibility APIs for decimal formatting.
  */
 
 #if !UCONFIG_NO_FORMATTING
 
 #include "unicode/dcfmtsym.h"
 #include "unicode/numfmt.h"
 #include "unicode/locid.h"
 #include "unicode/fpositer.h"
 #include "unicode/stringpiece.h"
 #include "unicode/curramt.h"
 #include "unicode/enumset.h"
 
 U_NAMESPACE_BEGIN
 
 class CurrencyPluralInfo;
 class CompactDecimalFormat;
 
 namespace number {
 class LocalizedNumberFormatter;
 namespace impl {
 class DecimalQuantity;
 struct DecimalFormatFields;
 class UFormattedNumberData;
 }
 }
 
 namespace numparse {
 namespace impl {
 class NumberParserImpl;
 }
 }
 
 /**
  * **IMPORTANT:** New users are strongly encouraged to see if
  * numberformatter.h fits their use case.  Although not deprecated, this header
  * is provided for backwards compatibility only.
  *
  * DecimalFormat is a concrete subclass of NumberFormat that formats decimal
  * numbers. It has a variety of features designed to make it possible to parse
  * and format numbers in any locale, including support for Western, Arabic, or
  * Indic digits.  It also supports different flavors of numbers, including
  * integers ("123"), fixed-point numbers ("123.4"), scientific notation
  * ("1.23E4"), percentages ("12%"), and currency amounts ("$123", "USD123",
  * "123 US dollars").  All of these flavors can be easily localized.
  *
  * To obtain a NumberFormat for a specific locale (including the default
  * locale) call one of NumberFormat's factory methods such as
  * createInstance(). Do not call the DecimalFormat constructors directly, unless
  * you know what you are doing, since the NumberFormat factory methods may
  * return subclasses other than DecimalFormat.
  *
  * **Example Usage**
  *
  * \code
  *     // Normally we would have a GUI with a menu for this
  *     int32_t locCount;
  *     const Locale* locales = NumberFormat::getAvailableLocales(locCount);
  *
  *     double myNumber = -1234.56;
  *     UErrorCode success = U_ZERO_ERROR;
  *     NumberFormat* form;
  *
  *     // Print out a number with the localized number, currency and percent
  *     // format for each locale.
  *     UnicodeString countryName;
  *     UnicodeString displayName;
  *     UnicodeString str;
  *     UnicodeString pattern;
  *     Formattable fmtable;
  *     for (int32_t j = 0; j < 3; ++j) {
  *         cout << endl << "FORMAT " << j << endl;
  *         for (int32_t i = 0; i < locCount; ++i) {
  *             if (locales[i].getCountry(countryName).size() == 0) {
  *                 // skip language-only
  *                 continue;
  *             }
  *             switch (j) {
  *             case 0:
  *                 form = NumberFormat::createInstance(locales[i], success ); break;
  *             case 1:
  *                 form = NumberFormat::createCurrencyInstance(locales[i], success ); break;
  *             default:
  *                 form = NumberFormat::createPercentInstance(locales[i], success ); break;
  *             }
  *             if (form) {
  *                 str.remove();
  *                 pattern = ((DecimalFormat*)form)->toPattern(pattern);
  *                 cout << locales[i].getDisplayName(displayName) << ": " << pattern;
  *                 cout << "  ->  " << form->format(myNumber,str) << endl;
  *                 form->parse(form->format(myNumber,str), fmtable, success);
  *                 delete form;
  *             }
  *         }
  *     }
  * \endcode
  *
  * **Another example use createInstance(style)**
  *
  * \code
  * // Print out a number using the localized number, currency,
  * // percent, scientific, integer, iso currency, and plural currency
  * // format for each locale</strong>
  * Locale* locale = new Locale("en", "US");
  * double myNumber = 1234.56;
  * UErrorCode success = U_ZERO_ERROR;
  * UnicodeString str;
  * Formattable fmtable;
  * for (int j=NumberFormat::kNumberStyle;
  *      j<=NumberFormat::kPluralCurrencyStyle;
  *      ++j) {
  *     NumberFormat* form = NumberFormat::createInstance(locale, j, success);
  *     str.remove();
  *     cout << "format result " << form->format(myNumber, str) << endl;
  *     format->parse(form->format(myNumber, str), fmtable, success);
  *     delete form;
  * }
  * \endcode
  *
  *
  * <p><strong>Patterns</strong>
  *
  * <p>A DecimalFormat consists of a <em>pattern</em> and a set of
  * <em>symbols</em>.  The pattern may be set directly using
  * applyPattern(), or indirectly using other API methods which
  * manipulate aspects of the pattern, such as the minimum number of integer
  * digits.  The symbols are stored in a DecimalFormatSymbols
  * object.  When using the NumberFormat factory methods, the
  * pattern and symbols are read from ICU's locale data.
  *
  * <p><strong>Special Pattern Characters</strong>
  *
  * <p>Many characters in a pattern are taken literally; they are matched during
  * parsing and output unchanged during formatting.  Special characters, on the
  * other hand, stand for other characters, strings, or classes of characters.
  * For example, the '#' character is replaced by a localized digit.  Often the
  * replacement character is the same as the pattern character; in the U.S. locale,
  * the ',' grouping character is replaced by ','.  However, the replacement is
  * still happening, and if the symbols are modified, the grouping character
  * changes.  Some special characters affect the behavior of the formatter by
  * their presence; for example, if the percent character is seen, then the
  * value is multiplied by 100 before being displayed.
  *
  * <p>To insert a special character in a pattern as a literal, that is, without
  * any special meaning, the character must be quoted.  There are some exceptions to
  * this which are noted below.
  *
  * <p>The characters listed here are used in non-localized patterns.  Localized
  * patterns use the corresponding characters taken from this formatter's
  * DecimalFormatSymbols object instead, and these characters lose
  * their special status.  Two exceptions are the currency sign and quote, which
  * are not localized.
  *
  * <table border=0 cellspacing=3 cellpadding=0>
  *   <tr bgcolor="#ccccff">
  *     <td align=left><strong>Symbol</strong>
  *     <td align=left><strong>Location</strong>
  *     <td align=left><strong>Localized?</strong>
  *     <td align=left><strong>Meaning</strong>
  *   <tr valign=top>
  *     <td><code>0</code>
  *     <td>Number
  *     <td>Yes
  *     <td>Digit
  *   <tr valign=top bgcolor="#eeeeff">
  *     <td><code>1-9</code>
  *     <td>Number
  *     <td>Yes
  *     <td>'1' through '9' indicate rounding.
  *   <tr valign=top>
  *     <td><code>\htmlonly&#x40;\endhtmlonly</code> <!--doxygen doesn't like @-->
  *     <td>Number
  *     <td>No
  *     <td>Significant digit
  *   <tr valign=top bgcolor="#eeeeff">
  *     <td><code>#</code>
  *     <td>Number
  *     <td>Yes
  *     <td>Digit, zero shows as absent
  *   <tr valign=top>
  *     <td><code>.</code>
  *     <td>Number
  *     <td>Yes
  *     <td>Decimal separator or monetary decimal separator
  *   <tr valign=top bgcolor="#eeeeff">
  *     <td><code>-</code>
  *     <td>Number
  *     <td>Yes
  *     <td>Minus sign
  *   <tr valign=top>
  *     <td><code>,</code>
  *     <td>Number
  *     <td>Yes
  *     <td>Grouping separator
  *   <tr valign=top bgcolor="#eeeeff">
  *     <td><code>E</code>
  *     <td>Number
  *     <td>Yes
  *     <td>Separates mantissa and exponent in scientific notation.
  *         <em>Need not be quoted in prefix or suffix.</em>
  *   <tr valign=top>
  *     <td><code>+</code>
  *     <td>Exponent
  *     <td>Yes
  *     <td>Prefix positive exponents with localized plus sign.
  *         <em>Need not be quoted in prefix or suffix.</em>
  *   <tr valign=top bgcolor="#eeeeff">
  *     <td><code>;</code>
  *     <td>Subpattern boundary
  *     <td>Yes
  *     <td>Separates positive and negative subpatterns
  *   <tr valign=top>
  *     <td><code>\%</code>
  *     <td>Prefix or suffix
  *     <td>Yes
  *     <td>Multiply by 100 and show as percentage
  *   <tr valign=top bgcolor="#eeeeff">
  *     <td><code>\\u2030</code>
  *     <td>Prefix or suffix
  *     <td>Yes
  *     <td>Multiply by 1000 and show as per mille
  *   <tr valign=top>
  *     <td><code>\htmlonly&curren;\endhtmlonly</code> (<code>\\u00A4</code>)
  *     <td>Prefix or suffix
  *     <td>No
  *     <td>Currency sign, replaced by currency symbol.  If
  *         doubled, replaced by international currency symbol.
  *         If tripled, replaced by currency plural names, for example,
  *         "US dollar" or "US dollars" for America.
  *         If present in a pattern, the monetary decimal separator
  *         is used instead of the decimal separator.
  *   <tr valign=top bgcolor="#eeeeff">
  *     <td><code>'</code>
  *     <td>Prefix or suffix
  *     <td>No
  *     <td>Used to quote special characters in a prefix or suffix,
  *         for example, <code>"'#'#"</code> formats 123 to
  *         <code>"#123"</code>.  To create a single quote
  *         itself, use two in a row: <code>"# o''clock"</code>.
  *   <tr valign=top>
  *     <td><code>*</code>
  *     <td>Prefix or suffix boundary
  *     <td>Yes
  *     <td>Pad escape, precedes pad character
  * </table>
  *
  * <p>A DecimalFormat pattern contains a positive and negative
  * subpattern, for example, "#,##0.00;(#,##0.00)".  Each subpattern has a
  * prefix, a numeric part, and a suffix.  If there is no explicit negative
  * subpattern, the negative subpattern is the localized minus sign prefixed to the
  * positive subpattern. That is, "0.00" alone is equivalent to "0.00;-0.00".  If there
  * is an explicit negative subpattern, it serves only to specify the negative
  * prefix and suffix; the number of digits, minimal digits, and other
  * characteristics are ignored in the negative subpattern. That means that
  * "#,##0.0#;(#)" has precisely the same result as "#,##0.0#;(#,##0.0#)".
  *
  * <p>The prefixes, suffixes, and various symbols used for infinity, digits,
  * thousands separators, decimal separators, etc. may be set to arbitrary
  * values, and they will appear properly during formatting.  However, care must
  * be taken that the symbols and strings do not conflict, or parsing will be
  * unreliable.  For example, either the positive and negative prefixes or the
  * suffixes must be distinct for parse() to be able
  * to distinguish positive from negative values.  Another example is that the
  * decimal separator and thousands separator should be distinct characters, or
  * parsing will be impossible.
  *
  * <p>The <em>grouping separator</em> is a character that separates clusters of
  * integer digits to make large numbers more legible.  It commonly used for
  * thousands, but in some locales it separates ten-thousands.  The <em>grouping
  * size</em> is the number of digits between the grouping separators, such as 3
  * for "100,000,000" or 4 for "1 0000 0000". There are actually two different
  * grouping sizes: One used for the least significant integer digits, the
  * <em>primary grouping size</em>, and one used for all others, the
  * <em>secondary grouping size</em>.  In most locales these are the same, but
  * sometimes they are different. For example, if the primary grouping interval
  * is 3, and the secondary is 2, then this corresponds to the pattern
  * "#,##,##0", and the number 123456789 is formatted as "12,34,56,789".  If a
  * pattern contains multiple grouping separators, the interval between the last
  * one and the end of the integer defines the primary grouping size, and the
  * interval between the last two defines the secondary grouping size. All others
  * are ignored, so "#,##,###,####" == "###,###,####" == "##,#,###,####".
  *
  * <p>Illegal patterns, such as "#.#.#" or "#.###,###", will cause
  * DecimalFormat to set a failing UErrorCode.
  *
  * <p><strong>Pattern BNF</strong>
  *
  * <pre>
  * pattern    := subpattern (';' subpattern)?
  * subpattern := prefix? number exponent? suffix?
  * number     := (integer ('.' fraction)?) | sigDigits
  * prefix     := '\\u0000'..'\\uFFFD' - specialCharacters
  * suffix     := '\\u0000'..'\\uFFFD' - specialCharacters
  * integer    := '#'* '0'* '0'
  * fraction   := '0'* '#'*
  * sigDigits  := '#'* '@' '@'* '#'*
  * exponent   := 'E' '+'? '0'* '0'
  * padSpec    := '*' padChar
  * padChar    := '\\u0000'..'\\uFFFD' - quote
  * &nbsp;
  * Notation:
  *   X*       0 or more instances of X
  *   X?       0 or 1 instances of X
  *   X|Y      either X or Y
  *   C..D     any character from C up to D, inclusive
  *   S-T      characters in S, except those in T
  * </pre>
  * The first subpattern is for positive numbers. The second (optional)
  * subpattern is for negative numbers.
  *
  * <p>Not indicated in the BNF syntax above:
  *
  * <ul><li>The grouping separator ',' can occur inside the integer and
  * sigDigits elements, between any two pattern characters of that
  * element, as long as the integer or sigDigits element is not
  * followed by the exponent element.
  *
  * <li>Two grouping intervals are recognized: That between the
  *     decimal point and the first grouping symbol, and that
  *     between the first and second grouping symbols. These
  *     intervals are identical in most locales, but in some
  *     locales they differ. For example, the pattern
  *     &quot;#,##,###&quot; formats the number 123456789 as
  *     &quot;12,34,56,789&quot;.</li>
  *
  * <li>The pad specifier <code>padSpec</code> may appear before the prefix,
  * after the prefix, before the suffix, after the suffix, or not at all.
  *
  * <li>In place of '0', the digits '1' through '9' may be used to
  * indicate a rounding increment.
  * </ul>
  *
  * <p><strong>Parsing</strong>
  *
  * <p>DecimalFormat parses all Unicode characters that represent
  * decimal digits, as defined by u_charDigitValue().  In addition,
  * DecimalFormat also recognizes as digits the ten consecutive
  * characters starting with the localized zero digit defined in the
  * DecimalFormatSymbols object.  During formatting, the
  * DecimalFormatSymbols-based digits are output.
  *
  * <p>During parsing, grouping separators are ignored if in lenient mode;
  * otherwise, if present, they must be in appropriate positions.
  *
  * <p>For currency parsing, the formatter is able to parse every currency
  * style formats no matter which style the formatter is constructed with.
  * For example, a formatter instance gotten from
  * NumberFormat.getInstance(ULocale, NumberFormat.CURRENCYSTYLE) can parse
  * formats such as "USD1.00" and "3.00 US dollars".
  *
  * <p>If parse(UnicodeString&,Formattable&,ParsePosition&)
  * fails to parse a string, it leaves the parse position unchanged.
  * The convenience method parse(UnicodeString&,Formattable&,UErrorCode&)
  * indicates parse failure by setting a failing
  * UErrorCode.
  *
  * <p><strong>Formatting</strong>
  *
  * <p>Formatting is guided by several parameters, all of which can be
  * specified either using a pattern or using the API.  The following
  * description applies to formats that do not use <a href="#sci">scientific
  * notation</a> or <a href="#sigdig">significant digits</a>.
  *
  * <ul><li>If the number of actual integer digits exceeds the
  * <em>maximum integer digits</em>, then only the least significant
  * digits are shown.  For example, 1997 is formatted as "97" if the
  * maximum integer digits is set to 2.
  *
  * <li>If the number of actual integer digits is less than the
  * <em>minimum integer digits</em>, then leading zeros are added.  For
  * example, 1997 is formatted as "01997" if the minimum integer digits
  * is set to 5.
  *
  * <li>If the number of actual fraction digits exceeds the <em>maximum
  * fraction digits</em>, then rounding is performed to the
  * maximum fraction digits.  For example, 0.125 is formatted as "0.12"
  * if the maximum fraction digits is 2.  This behavior can be changed
  * by specifying a rounding increment and/or a rounding mode.
  *
  * <li>If the number of actual fraction digits is less than the
  * <em>minimum fraction digits</em>, then trailing zeros are added.
  * For example, 0.125 is formatted as "0.1250" if the minimum fraction
  * digits is set to 4.
  *
  * <li>Trailing fractional zeros are not displayed if they occur
  * <em>j</em> positions after the decimal, where <em>j</em> is less
  * than the maximum fraction digits. For example, 0.10004 is
  * formatted as "0.1" if the maximum fraction digits is four or less.
  * </ul>
  *
  * <p><strong>Special Values</strong>
  *
  * <p><code>NaN</code> is represented as a single character, typically
  * <code>\\uFFFD</code>.  This character is determined by the
  * DecimalFormatSymbols object.  This is the only value for which
  * the prefixes and suffixes are not used.
  *
  * <p>Infinity is represented as a single character, typically
  * <code>\\u221E</code>, with the positive or negative prefixes and suffixes
  * applied.  The infinity character is determined by the
  * DecimalFormatSymbols object.
  *
  * <a name="sci"><strong>Scientific Notation</strong></a>
  *
  * <p>Numbers in scientific notation are expressed as the product of a mantissa
  * and a power of ten, for example, 1234 can be expressed as 1.234 x 10<sup>3</sup>. The
  * mantissa is typically in the half-open interval [1.0, 10.0) or sometimes [0.0, 1.0),
  * but it need not be.  DecimalFormat supports arbitrary mantissas.
  * DecimalFormat can be instructed to use scientific
  * notation through the API or through the pattern.  In a pattern, the exponent
  * character immediately followed by one or more digit characters indicates
  * scientific notation.  Example: "0.###E0" formats the number 1234 as
  * "1.234E3".
  *
  * <ul>
  * <li>The number of digit characters after the exponent character gives the
  * minimum exponent digit count.  There is no maximum.  Negative exponents are
  * formatted using the localized minus sign, <em>not</em> the prefix and suffix
  * from the pattern.  This allows patterns such as "0.###E0 m/s".  To prefix
  * positive exponents with a localized plus sign, specify '+' between the
  * exponent and the digits: "0.###E+0" will produce formats "1E+1", "1E+0",
  * "1E-1", etc.  (In localized patterns, use the localized plus sign rather than
  * '+'.)
  *
  * <li>The minimum number of integer digits is achieved by adjusting the
  * exponent.  Example: 0.00123 formatted with "00.###E0" yields "12.3E-4".  This
  * only happens if there is no maximum number of integer digits.  If there is a
  * maximum, then the minimum number of integer digits is fixed at one.
  *
  * <li>The maximum number of integer digits, if present, specifies the exponent
  * grouping.  The most common use of this is to generate <em>engineering
  * notation</em>, in which the exponent is a multiple of three, e.g.,
  * "##0.###E0".  The number 12345 is formatted using "##0.####E0" as "12.345E3".
  *
  * <li>When using scientific notation, the formatter controls the
  * digit counts using significant digits logic.  The maximum number of
  * significant digits limits the total number of integer and fraction
  * digits that will be shown in the mantissa; it does not affect
  * parsing.  For example, 12345 formatted with "##0.##E0" is "12.3E3".
  * See the section on significant digits for more details.
  *
  * <li>The number of significant digits shown is determined as
  * follows: If areSignificantDigitsUsed() returns false, then the
  * minimum number of significant digits shown is one, and the maximum
  * number of significant digits shown is the sum of the <em>minimum
  * integer</em> and <em>maximum fraction</em> digits, and is
  * unaffected by the maximum integer digits.  If this sum is zero,
  * then all significant digits are shown.  If
  * areSignificantDigitsUsed() returns true, then the significant digit
  * counts are specified by getMinimumSignificantDigits() and
  * getMaximumSignificantDigits().  In this case, the number of
  * integer digits is fixed at one, and there is no exponent grouping.
  *
  * <li>Exponential patterns may not contain grouping separators.
  * </ul>
  *
  * <a name="sigdig"><strong>Significant Digits</strong></a>
  *
  * <code>DecimalFormat</code> has two ways of controlling how many
  * digits are shows: (a) significant digits counts, or (b) integer and
  * fraction digit counts.  Integer and fraction digit counts are
  * described above.  When a formatter is using significant digits
  * counts, the number of integer and fraction digits is not specified
  * directly, and the formatter settings for these counts are ignored.
  * Instead, the formatter uses however many integer and fraction
  * digits are required to display the specified number of significant
  * digits.  Examples:
  *
  * <table border=0 cellspacing=3 cellpadding=0>
  *   <tr bgcolor="#ccccff">
  *     <td align=left>Pattern
  *     <td align=left>Minimum significant digits
  *     <td align=left>Maximum significant digits
  *     <td align=left>Number
  *     <td align=left>Output of format()
  *   <tr valign=top>
  *     <td><code>\@\@\@</code>
  *     <td>3
  *     <td>3
  *     <td>12345
  *     <td><code>12300</code>
  *   <tr valign=top bgcolor="#eeeeff">
  *     <td><code>\@\@\@</code>
  *     <td>3
  *     <td>3
  *     <td>0.12345
  *     <td><code>0.123</code>
  *   <tr valign=top>
  *     <td><code>\@\@##</code>
  *     <td>2
  *     <td>4
  *     <td>3.14159
  *     <td><code>3.142</code>
  *   <tr valign=top bgcolor="#eeeeff">
  *     <td><code>\@\@##</code>
  *     <td>2
  *     <td>4
  *     <td>1.23004
  *     <td><code>1.23</code>
  * </table>
  *
  * <ul>
  * <li>Significant digit counts may be expressed using patterns that
  * specify a minimum and maximum number of significant digits.  These
  * are indicated by the <code>'@'</code> and <code>'#'</code>
  * characters.  The minimum number of significant digits is the number
  * of <code>'@'</code> characters.  The maximum number of significant
  * digits is the number of <code>'@'</code> characters plus the number
  * of <code>'#'</code> characters following on the right.  For
  * example, the pattern <code>"@@@"</code> indicates exactly 3
  * significant digits.  The pattern <code>"@##"</code> indicates from
  * 1 to 3 significant digits.  Trailing zero digits to the right of
  * the decimal separator are suppressed after the minimum number of
  * significant digits have been shown.  For example, the pattern
  * <code>"@##"</code> formats the number 0.1203 as
  * <code>"0.12"</code>.
  *
  * <li>If a pattern uses significant digits, it may not contain a
  * decimal separator, nor the <code>'0'</code> pattern character.
  * Patterns such as <code>"@00"</code> or <code>"@.###"</code> are
  * disallowed.
  *
  * <li>Any number of <code>'#'</code> characters may be prepended to
  * the left of the leftmost <code>'@'</code> character.  These have no
  * effect on the minimum and maximum significant digits counts, but
  * may be used to position grouping separators.  For example,
  * <code>"#,#@#"</code> indicates a minimum of one significant digits,
  * a maximum of two significant digits, and a grouping size of three.
  *
  * <li>In order to enable significant digits formatting, use a pattern
  * containing the <code>'@'</code> pattern character.  Alternatively,
  * call setSignificantDigitsUsed(true).
  *
  * <li>In order to disable significant digits formatting, use a
  * pattern that does not contain the <code>'@'</code> pattern
  * character. Alternatively, call setSignificantDigitsUsed(false).
  *
  * <li>The number of significant digits has no effect on parsing.
  *
  * <li>Significant digits may be used together with exponential notation. Such
  * patterns are equivalent to a normal exponential pattern with a minimum and
  * maximum integer digit count of one, a minimum fraction digit count of
  * <code>getMinimumSignificantDigits() - 1</code>, and a maximum fraction digit
  * count of <code>getMaximumSignificantDigits() - 1</code>. For example, the
  * pattern <code>"@@###E0"</code> is equivalent to <code>"0.0###E0"</code>.
  *
  * <li>If significant digits are in use, then the integer and fraction
  * digit counts, as set via the API, are ignored.  If significant
  * digits are not in use, then the significant digit counts, as set via
  * the API, are ignored.
  *
  * </ul>
  *
  * <p><strong>Padding</strong>
  *
  * <p>DecimalFormat supports padding the result of
  * format() to a specific width.  Padding may be specified either
  * through the API or through the pattern syntax.  In a pattern the pad escape
  * character, followed by a single pad character, causes padding to be parsed
  * and formatted.  The pad escape character is '*' in unlocalized patterns, and
  * can be localized using DecimalFormatSymbols::setSymbol() with a
  * DecimalFormatSymbols::kPadEscapeSymbol
  * selector.  For example, <code>"$*x#,##0.00"</code> formats 123 to
  * <code>"$xx123.00"</code>, and 1234 to <code>"$1,234.00"</code>.
  *
  * <ul>
  * <li>When padding is in effect, the width of the positive subpattern,
  * including prefix and suffix, determines the format width.  For example, in
  * the pattern <code>"* #0 o''clock"</code>, the format width is 10.
  *
  * <li>The width is counted in 16-bit code units (char16_ts).
  *
  * <li>Some parameters which usually do not matter have meaning when padding is
  * used, because the pattern width is significant with padding.  In the pattern
  * "* ##,##,#,##0.##", the format width is 14.  The initial characters "##,##,"
  * do not affect the grouping size or maximum integer digits, but they do affect
  * the format width.
  *
  * <li>Padding may be inserted at one of four locations: before the prefix,
  * after the prefix, before the suffix, or after the suffix.  If padding is
  * specified in any other location, applyPattern()
  * sets a failing UErrorCode.  If there is no prefix,
  * before the prefix and after the prefix are equivalent, likewise for the
  * suffix.
  *
  * <li>When specified in a pattern, the 32-bit code point immediately
  * following the pad escape is the pad character. This may be any character,
  * including a special pattern character. That is, the pad escape
  * <em>escapes</em> the following character. If there is no character after
  * the pad escape, then the pattern is illegal.
  *
  * </ul>
  *
  * <p><strong>Rounding</strong>
  *
  * <p>DecimalFormat supports rounding to a specific increment.  For
  * example, 1230 rounded to the nearest 50 is 1250.  1.234 rounded to the
  * nearest 0.65 is 1.3.  The rounding increment may be specified through the API
  * or in a pattern.  To specify a rounding increment in a pattern, include the
  * increment in the pattern itself.  "#,#50" specifies a rounding increment of
  * 50.  "#,##0.05" specifies a rounding increment of 0.05.
  *
  * <p>In the absence of an explicit rounding increment numbers are
  * rounded to their formatted width.
  *
  * <ul>
  * <li>Rounding only affects the string produced by formatting.  It does
  * not affect parsing or change any numerical values.
  *
  * <li>A <em>rounding mode</em> determines how values are rounded; see
  * DecimalFormat::ERoundingMode.  The default rounding mode is
  * DecimalFormat::kRoundHalfEven.  The rounding mode can only be set
  * through the API; it can not be set with a pattern.
  *
  * <li>Some locales use rounding in their currency formats to reflect the
  * smallest currency denomination.
  *
  * <li>In a pattern, digits '1' through '9' specify rounding, but otherwise
  * behave identically to digit '0'.
  * </ul>
  *
  * <p><strong>Synchronization</strong>
  *
  * <p>DecimalFormat objects are not synchronized.  Multiple
  * threads should not access one formatter concurrently.
  *
  * <p><strong>Subclassing</strong>
  *
  * <p><em>User subclasses are not supported.</em> While clients may write
  * subclasses, such code will not necessarily work and will not be
  * guaranteed to work stably from release to release.
  */
 class U_I18N_API DecimalFormat : public NumberFormat {
   public:
     /**
      * Pad position.
      * @stable ICU 2.4
      */
     enum EPadPosition {
         kPadBeforePrefix, kPadAfterPrefix, kPadBeforeSuffix, kPadAfterSuffix
     };
 
     /**
      * Create a DecimalFormat using the default pattern and symbols
      * for the default locale. This is a convenient way to obtain a
      * DecimalFormat when internationalization is not the main concern.
      * <P>
      * To obtain standard formats for a given locale, use the factory methods
      * on NumberFormat such as createInstance. These factories will
      * return the most appropriate sub-class of NumberFormat for a given
      * locale.
      * <p>
      * <strong>NOTE:</strong> New users are strongly encouraged to use
      * #icu::number::NumberFormatter instead of DecimalFormat.
      * @param status    Output param set to success/failure code. If the
      *                  pattern is invalid this will be set to a failure code.
      * @stable ICU 2.0
      */
     DecimalFormat(UErrorCode& status);
 
     /**
      * Create a DecimalFormat from the given pattern and the symbols
      * for the default locale. This is a convenient way to obtain a
      * DecimalFormat when internationalization is not the main concern.
      * <P>
      * To obtain standard formats for a given locale, use the factory methods
      * on NumberFormat such as createInstance. These factories will
      * return the most appropriate sub-class of NumberFormat for a given
      * locale.
      * <p>
      * <strong>NOTE:</strong> New users are strongly encouraged to use
      * #icu::number::NumberFormatter instead of DecimalFormat.
      * @param pattern   A non-localized pattern string.
      * @param status    Output param set to success/failure code. If the
      *                  pattern is invalid this will be set to a failure code.
      * @stable ICU 2.0
      */
     DecimalFormat(const UnicodeString& pattern, UErrorCode& status);
 
     /**
      * Create a DecimalFormat from the given pattern and symbols.
      * Use this constructor when you need to completely customize the
      * behavior of the format.
      * <P>
      * To obtain standard formats for a given
      * locale, use the factory methods on NumberFormat such as
      * createInstance or createCurrencyInstance. If you need only minor adjustments
      * to a standard format, you can modify the format returned by
      * a NumberFormat factory method.
      * <p>
      * <strong>NOTE:</strong> New users are strongly encouraged to use
      * #icu::number::NumberFormatter instead of DecimalFormat.
      *
      * @param pattern           a non-localized pattern string
      * @param symbolsToAdopt    the set of symbols to be used.  The caller should not
      *                          delete this object after making this call.
      * @param status            Output param set to success/failure code. If the
      *                          pattern is invalid this will be set to a failure code.
      * @stable ICU 2.0
      */
     DecimalFormat(const UnicodeString& pattern, DecimalFormatSymbols* symbolsToAdopt, UErrorCode& status);
 
 #ifndef U_HIDE_INTERNAL_API
 
     /**
      * This API is for ICU use only.
      * Create a DecimalFormat from the given pattern, symbols, and style.
      *
      * @param pattern           a non-localized pattern string
      * @param symbolsToAdopt    the set of symbols to be used.  The caller should not
      *                          delete this object after making this call.
      * @param style             style of decimal format
      * @param status            Output param set to success/failure code. If the
      *                          pattern is invalid this will be set to a failure code.
      * @internal
      */
     DecimalFormat(const UnicodeString& pattern, DecimalFormatSymbols* symbolsToAdopt,
                   UNumberFormatStyle style, UErrorCode& status);
 
 #if UCONFIG_HAVE_PARSEALLINPUT
 
     /**
      * @internal
      */
     void setParseAllInput(UNumberFormatAttributeValue value);
 
 #endif
 
 #endif  /* U_HIDE_INTERNAL_API */
 
   private:
 
     /**
      * Internal constructor for DecimalFormat; sets up internal fields. All public constructors should
      * call this constructor.
      */
     DecimalFormat(const DecimalFormatSymbols* symbolsToAdopt, UErrorCode& status);
 
   public:
 
     /**
      * Set an integer attribute on this DecimalFormat.
      * May return U_UNSUPPORTED_ERROR if this instance does not support
      * the specified attribute.
      * @param attr the attribute to set
      * @param newValue new value
      * @param status the error type
      * @return *this - for chaining (example: format.setAttribute(...).setAttribute(...) )
      * @stable ICU 51
      */
     virtual DecimalFormat& setAttribute(UNumberFormatAttribute attr, int32_t newValue, UErrorCode& status);
 
     /**
      * Get an integer
      * May return U_UNSUPPORTED_ERROR if this instance does not support
      * the specified attribute.
      * @param attr the attribute to set
      * @param status the error type
      * @return the attribute value. Undefined if there is an error.
      * @stable ICU 51
      */
     virtual int32_t getAttribute(UNumberFormatAttribute attr, UErrorCode& status) const;
 
 
     /**
      * Set whether or not grouping will be used in this format.
      * @param newValue    True, grouping will be used in this format.
      * @see getGroupingUsed
      * @stable ICU 53
      */
     void setGroupingUsed(UBool newValue) override;
 
     /**
      * Sets whether or not numbers should be parsed as integers only.
      * @param value    set True, this format will parse numbers as integers
      *                 only.
      * @see isParseIntegerOnly
      * @stable ICU 53
      */
     void setParseIntegerOnly(UBool value) override;
 
     /**
      * Sets whether lenient parsing should be enabled (it is off by default).
      *
      * @param enable \c true if lenient parsing should be used,
      *               \c false otherwise.
      * @stable ICU 4.8
      */
     void setLenient(UBool enable) override;
 
     /**
      * Create a DecimalFormat from the given pattern and symbols.
      * Use this constructor when you need to completely customize the
      * behavior of the format.
      * <P>
      * To obtain standard formats for a given
      * locale, use the factory methods on NumberFormat such as
      * createInstance or createCurrencyInstance. If you need only minor adjustments
      * to a standard format, you can modify the format returned by
      * a NumberFormat factory method.
      * <p>
      * <strong>NOTE:</strong> New users are strongly encouraged to use
      * #icu::number::NumberFormatter instead of DecimalFormat.
      *
      * @param pattern           a non-localized pattern string
      * @param symbolsToAdopt    the set of symbols to be used.  The caller should not
      *                          delete this object after making this call.
      * @param parseError        Output param to receive errors occurred during parsing
      * @param status            Output param set to success/failure code. If the
      *                          pattern is invalid this will be set to a failure code.
      * @stable ICU 2.0
      */
     DecimalFormat(const UnicodeString& pattern, DecimalFormatSymbols* symbolsToAdopt,
                   UParseError& parseError, UErrorCode& status);
 
     /**
      * Create a DecimalFormat from the given pattern and symbols.
      * Use this constructor when you need to completely customize the
      * behavior of the format.
      * <P>
      * To obtain standard formats for a given
      * locale, use the factory methods on NumberFormat such as
      * createInstance or createCurrencyInstance. If you need only minor adjustments
      * to a standard format, you can modify the format returned by
      * a NumberFormat factory method.
      * <p>
      * <strong>NOTE:</strong> New users are strongly encouraged to use
      * #icu::number::NumberFormatter instead of DecimalFormat.
      *
      * @param pattern           a non-localized pattern string
      * @param symbols   the set of symbols to be used
      * @param status            Output param set to success/failure code. If the
      *                          pattern is invalid this will be set to a failure code.
      * @stable ICU 2.0
      */
     DecimalFormat(const UnicodeString& pattern, const DecimalFormatSymbols& symbols, UErrorCode& status);
 
     /**
      * Copy constructor.
      *
      * @param source    the DecimalFormat object to be copied from.
      * @stable ICU 2.0
      */
     DecimalFormat(const DecimalFormat& source);
 
     /**
      * Assignment operator.
      *
      * @param rhs    the DecimalFormat object to be copied.
      * @stable ICU 2.0
      */
     DecimalFormat& operator=(const DecimalFormat& rhs);
 
     /**
      * Destructor.
      * @stable ICU 2.0
      */
     ~DecimalFormat() override;
 
     /**
      * Clone this Format object polymorphically. The caller owns the
      * result and should delete it when done.
      *
      * @return    a polymorphic copy of this DecimalFormat.
      * @stable ICU 2.0
      */
     DecimalFormat* clone() const override;
 
     /**
      * Return true if the given Format objects are semantically equal.
      * Objects of different subclasses are considered unequal.
      *
      * @param other    the object to be compared with.
      * @return         true if the given Format objects are semantically equal.
      * @stable ICU 2.0
      */
     bool operator==(const Format& other) const override;
 
 
     using NumberFormat::format;
 
     /**
      * Format a double or long number using base-10 representation.
      *
      * @param number    The value to be formatted.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param pos       On input: an alignment field, if desired.
      *                  On output: the offsets of the alignment field.
      * @return          Reference to 'appendTo' parameter.
      * @stable ICU 2.0
      */
     UnicodeString& format(double number, UnicodeString& appendTo, FieldPosition& pos) const override;
 
 #ifndef U_HIDE_INTERNAL_API
     /**
      * Format a double or long number using base-10 representation.
      *
      * @param number    The value to be formatted.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param pos       On input: an alignment field, if desired.
      *                  On output: the offsets of the alignment field.
      * @param status
      * @return          Reference to 'appendTo' parameter.
      * @internal
      */
     UnicodeString& format(double number, UnicodeString& appendTo, FieldPosition& pos,
                           UErrorCode& status) const override;
 #endif  /* U_HIDE_INTERNAL_API */
 
     /**
      * Format a double or long number using base-10 representation.
      *
      * @param number    The value to be formatted.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param posIter   On return, can be used to iterate over positions
      *                  of fields generated by this format call.
      *                  Can be nullptr.
      * @param status    Output param filled with success/failure status.
      * @return          Reference to 'appendTo' parameter.
      * @stable ICU 4.4
      */
     UnicodeString& format(double number, UnicodeString& appendTo, FieldPositionIterator* posIter,
                           UErrorCode& status) const override;
 
     /**
      * Format a long number using base-10 representation.
      *
      * @param number    The value to be formatted.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param pos       On input: an alignment field, if desired.
      *                  On output: the offsets of the alignment field.
      * @return          Reference to 'appendTo' parameter.
      * @stable ICU 2.0
      */
     UnicodeString& format(int32_t number, UnicodeString& appendTo, FieldPosition& pos) const override;
 
 #ifndef U_HIDE_INTERNAL_API
     /**
      * Format a long number using base-10 representation.
      *
      * @param number    The value to be formatted.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param pos       On input: an alignment field, if desired.
      *                  On output: the offsets of the alignment field.
      * @param status    Output param filled with success/failure status.
      * @return          Reference to 'appendTo' parameter.
      * @internal
      */
     UnicodeString& format(int32_t number, UnicodeString& appendTo, FieldPosition& pos,
                           UErrorCode& status) const override;
 #endif  /* U_HIDE_INTERNAL_API */
 
     /**
      * Format a long number using base-10 representation.
      *
      * @param number    The value to be formatted.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param posIter   On return, can be used to iterate over positions
      *                  of fields generated by this format call.
      *                  Can be nullptr.
      * @param status    Output param filled with success/failure status.
      * @return          Reference to 'appendTo' parameter.
      * @stable ICU 4.4
      */
     UnicodeString& format(int32_t number, UnicodeString& appendTo, FieldPositionIterator* posIter,
                           UErrorCode& status) const override;
 
     /**
      * Format an int64 number using base-10 representation.
      *
      * @param number    The value to be formatted.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param pos       On input: an alignment field, if desired.
      *                  On output: the offsets of the alignment field.
      * @return          Reference to 'appendTo' parameter.
      * @stable ICU 2.8
      */
     UnicodeString& format(int64_t number, UnicodeString& appendTo, FieldPosition& pos) const override;
 
 #ifndef U_HIDE_INTERNAL_API
     /**
      * Format an int64 number using base-10 representation.
      *
      * @param number    The value to be formatted.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param pos       On input: an alignment field, if desired.
      *                  On output: the offsets of the alignment field.
      * @param status    Output param filled with success/failure status.
      * @return          Reference to 'appendTo' parameter.
      * @internal
      */
     UnicodeString& format(int64_t number, UnicodeString& appendTo, FieldPosition& pos,
                           UErrorCode& status) const override;
 #endif  /* U_HIDE_INTERNAL_API */
 
     /**
      * Format an int64 number using base-10 representation.
      *
      * @param number    The value to be formatted.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param posIter   On return, can be used to iterate over positions
      *                  of fields generated by this format call.
      *                  Can be nullptr.
      * @param status    Output param filled with success/failure status.
      * @return          Reference to 'appendTo' parameter.
      * @stable ICU 4.4
      */
     UnicodeString& format(int64_t number, UnicodeString& appendTo, FieldPositionIterator* posIter,
                           UErrorCode& status) const override;
 
     /**
      * Format a decimal number.
      * The syntax of the unformatted number is a "numeric string"
      * as defined in the Decimal Arithmetic Specification, available at
      * http://speleotrove.com/decimal
      *
      * @param number    The unformatted number, as a string.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param posIter   On return, can be used to iterate over positions
      *                  of fields generated by this format call.
      *                  Can be nullptr.
      * @param status    Output param filled with success/failure status.
      * @return          Reference to 'appendTo' parameter.
      * @stable ICU 4.4
      */
     UnicodeString& format(StringPiece number, UnicodeString& appendTo, FieldPositionIterator* posIter,
                           UErrorCode& status) const override;
 
 #ifndef U_HIDE_INTERNAL_API
 
     /**
      * Format a decimal number.
      * The number is a DecimalQuantity wrapper onto a floating point decimal number.
      * The default implementation in NumberFormat converts the decimal number
      * to a double and formats that.
      *
      * @param number    The number, a DecimalQuantity format Decimal Floating Point.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param posIter   On return, can be used to iterate over positions
      *                  of fields generated by this format call.
      * @param status    Output param filled with success/failure status.
      * @return          Reference to 'appendTo' parameter.
      * @internal
      */
     UnicodeString& format(const number::impl::DecimalQuantity& number, UnicodeString& appendTo,
                           FieldPositionIterator* posIter, UErrorCode& status) const override;
 
     /**
      * Format a decimal number.
      * The number is a DecimalQuantity wrapper onto a floating point decimal number.
      * The default implementation in NumberFormat converts the decimal number
      * to a double and formats that.
      *
      * @param number    The number, a DecimalQuantity format Decimal Floating Point.
      * @param appendTo  Output parameter to receive result.
      *                  Result is appended to existing contents.
      * @param pos       On input: an alignment field, if desired.
      *                  On output: the offsets of the alignment field.
      * @param status    Output param filled with success/failure status.
      * @return          Reference to 'appendTo' parameter.
      * @internal
      */
     UnicodeString& format(const number::impl::DecimalQuantity& number, UnicodeString& appendTo,
                           FieldPosition& pos, UErrorCode& status) const override;
 
 #endif // U_HIDE_INTERNAL_API
 
     using NumberFormat::parse;
 
     /**
      * Parse the given string using this object's choices. The method
      * does string comparisons to try to find an optimal match.
      * If no object can be parsed, index is unchanged, and nullptr is
      * returned.  The result is returned as the most parsimonious
      * type of Formattable that will accommodate all of the
      * necessary precision.  For example, if the result is exactly 12,
      * it will be returned as a long.  However, if it is 1.5, it will
      * be returned as a double.
      *
      * @param text           The text to be parsed.
      * @param result         Formattable to be set to the parse result.
      *                       If parse fails, return contents are undefined.
      * @param parsePosition  The position to start parsing at on input.
      *                       On output, moved to after the last successfully
      *                       parse character. On parse failure, does not change.
      * @see Formattable
      * @stable ICU 2.0
      */
     void parse(const UnicodeString& text, Formattable& result,
                ParsePosition& parsePosition) const override;
 
     /**
      * Parses text from the given string as a currency amount.  Unlike
      * the parse() method, this method will attempt to parse a generic
      * currency name, searching for a match of this object's locale's
      * currency display names, or for a 3-letter ISO currency code.
      * This method will fail if this format is not a currency format,
      * that is, if it does not contain the currency pattern symbol
      * (U+00A4) in its prefix or suffix.
      *
      * @param text the string to parse
      * @param pos  input-output position; on input, the position within text
      *             to match; must have 0 <= pos.getIndex() < text.length();
      *             on output, the position after the last matched character.
      *             If the parse fails, the position in unchanged upon output.
      * @return     if parse succeeds, a pointer to a newly-created CurrencyAmount
      *             object (owned by the caller) containing information about
      *             the parsed currency; if parse fails, this is nullptr.
      * @stable ICU 49
      */
     CurrencyAmount* parseCurrency(const UnicodeString& text, ParsePosition& pos) const override;
 
     /**
      * Returns the decimal format symbols, which is generally not changed
      * by the programmer or user.
      * @return desired DecimalFormatSymbols
      * @see DecimalFormatSymbols
      * @stable ICU 2.0
      */
     virtual const DecimalFormatSymbols* getDecimalFormatSymbols(void) const;
 
     /**
      * Sets the decimal format symbols, which is generally not changed
      * by the programmer or user.
      * @param symbolsToAdopt DecimalFormatSymbols to be adopted.
      * @stable ICU 2.0
      */
     virtual void adoptDecimalFormatSymbols(DecimalFormatSymbols* symbolsToAdopt);
 
     /**
      * Sets the decimal format symbols, which is generally not changed
      * by the programmer or user.
      * @param symbols DecimalFormatSymbols.
      * @stable ICU 2.0
      */
     virtual void setDecimalFormatSymbols(const DecimalFormatSymbols& symbols);
 
 
     /**
      * Returns the currency plural format information,
      * which is generally not changed by the programmer or user.
      * @return desired CurrencyPluralInfo
      * @stable ICU 4.2
      */
     virtual const CurrencyPluralInfo* getCurrencyPluralInfo(void) const;
 
     /**
      * Sets the currency plural format information,
      * which is generally not changed by the programmer or user.
      * @param toAdopt CurrencyPluralInfo to be adopted.
      * @stable ICU 4.2
      */
     virtual void adoptCurrencyPluralInfo(CurrencyPluralInfo* toAdopt);
 
     /**
      * Sets the currency plural format information,
      * which is generally not changed by the programmer or user.
      * @param info Currency Plural Info.
      * @stable ICU 4.2
      */
     virtual void setCurrencyPluralInfo(const CurrencyPluralInfo& info);
 
 
     /**
      * Get the positive prefix.
      *
      * @param result    Output param which will receive the positive prefix.
      * @return          A reference to 'result'.
      * Examples: +123, $123, sFr123
      * @stable ICU 2.0
      */
     UnicodeString& getPositivePrefix(UnicodeString& result) const;
 
     /**
      * Set the positive prefix.
      *
      * @param newValue    the new value of the the positive prefix to be set.
      * Examples: +123, $123, sFr123
      * @stable ICU 2.0
      */
     virtual void setPositivePrefix(const UnicodeString& newValue);
 
     /**
      * Get the negative prefix.
      *
      * @param result    Output param which will receive the negative prefix.
      * @return          A reference to 'result'.
      * Examples: -123, ($123) (with negative suffix), sFr-123
      * @stable ICU 2.0
      */
     UnicodeString& getNegativePrefix(UnicodeString& result) const;
 
     /**
      * Set the negative prefix.
      *
      * @param newValue    the new value of the the negative prefix to be set.
      * Examples: -123, ($123) (with negative suffix), sFr-123
      * @stable ICU 2.0
      */
     virtual void setNegativePrefix(const UnicodeString& newValue);
 
     /**
      * Get the positive suffix.
      *
      * @param result    Output param which will receive the positive suffix.
      * @return          A reference to 'result'.
      * Example: 123%
      * @stable ICU 2.0
      */
     UnicodeString& getPositiveSuffix(UnicodeString& result) const;
 
     /**
      * Set the positive suffix.
      *
      * @param newValue    the new value of the positive suffix to be set.
      * Example: 123%
      * @stable ICU 2.0
      */
     virtual void setPositiveSuffix(const UnicodeString& newValue);
 
     /**
      * Get the negative suffix.
      *
      * @param result    Output param which will receive the negative suffix.
      * @return          A reference to 'result'.
      * Examples: -123%, ($123) (with positive suffixes)
      * @stable ICU 2.0
      */
     UnicodeString& getNegativeSuffix(UnicodeString& result) const;
 
     /**
      * Set the negative suffix.
      *
      * @param newValue    the new value of the negative suffix to be set.
      * Examples: 123%
      * @stable ICU 2.0
      */
     virtual void setNegativeSuffix(const UnicodeString& newValue);
 
     /**
      * Whether to show the plus sign on positive (non-negative) numbers; for example, "+12"
      *
      * For more control over sign display, use NumberFormatter.
      *
      * @return Whether the sign is shown on positive numbers and zero.
      * @stable ICU 64
      */
     UBool isSignAlwaysShown() const;
 
     /**
      * Set whether to show the plus sign on positive (non-negative) numbers; for example, "+12".
      *
      * For more control over sign display, use NumberFormatter.
      *
      * @param value true to always show a sign; false to hide the sign on positive numbers and zero.
      * @stable ICU 64
      */
     void setSignAlwaysShown(UBool value);
 
     /**
      * Get the multiplier for use in percent, permill, etc.
      * For a percentage, set the suffixes to have "%" and the multiplier to be 100.
      * (For Arabic, use arabic percent symbol).
      * For a permill, set the suffixes to have "\\u2031" and the multiplier to be 1000.
      *
      * The number may also be multiplied by a power of ten; see getMultiplierScale().
      *
      * @return    the multiplier for use in percent, permill, etc.
      * Examples: with 100, 1.23 -> "123", and "123" -> 1.23
      * @stable ICU 2.0
      */
     int32_t getMultiplier(void) const;
 
     /**
      * Set the multiplier for use in percent, permill, etc.
      * For a percentage, set the suffixes to have "%" and the multiplier to be 100.
      * (For Arabic, use arabic percent symbol).
      * For a permill, set the suffixes to have "\\u2031" and the multiplier to be 1000.
      *
      * This method only supports integer multipliers. To multiply by a non-integer, pair this
      * method with setMultiplierScale().
      *
      * @param newValue    the new value of the multiplier for use in percent, permill, etc.
      * Examples: with 100, 1.23 -> "123", and "123" -> 1.23
      * @stable ICU 2.0
      */
     virtual void setMultiplier(int32_t newValue);
 
     /**
      * Gets the power of ten by which number should be multiplied before formatting, which
      * can be combined with setMultiplier() to multiply by any arbitrary decimal value.
      *
      * A multiplier scale of 2 corresponds to multiplication by 100, and a multiplier scale
      * of -2 corresponds to multiplication by 0.01.
      *
      * This method is analogous to UNUM_SCALE in getAttribute.
      *
      * @return    the current value of the power-of-ten multiplier.
      * @stable ICU 62
      */
     int32_t getMultiplierScale(void) const;
 
     /**
      * Sets a power of ten by which number should be multiplied before formatting, which
      * can be combined with setMultiplier() to multiply by any arbitrary decimal value.
      *
      * A multiplier scale of 2 corresponds to multiplication by 100, and a multiplier scale
      * of -2 corresponds to multiplication by 0.01.
      *
      * For example, to multiply numbers by 0.5 before formatting, you can do:
      *
      * <pre>
      * df.setMultiplier(5);
      * df.setMultiplierScale(-1);
      * </pre>
      *
      * This method is analogous to UNUM_SCALE in setAttribute.
      *
      * @param newValue    the new value of the power-of-ten multiplier.
      * @stable ICU 62
      */
     void setMultiplierScale(int32_t newValue);
 
     /**
      * Get the rounding increment.
      * @return A positive rounding increment, or 0.0 if a custom rounding
      * increment is not in effect.
      * @see #setRoundingIncrement
      * @see #getRoundingMode
      * @see #setRoundingMode
      * @stable ICU 2.0
      */
     virtual double getRoundingIncrement(void) const;
 
     /**
      * Set the rounding increment.  In the absence of a rounding increment,
      *    numbers will be rounded to the number of digits displayed.
      * @param newValue A positive rounding increment, or 0.0 to
      * use the default rounding increment.
      * Negative increments are equivalent to 0.0.
      * @see #getRoundingIncrement
      * @see #getRoundingMode
      * @see #setRoundingMode
      * @stable ICU 2.0
      */
     virtual void setRoundingIncrement(double newValue);
 
     /**
      * Get the rounding mode.
      * @return A rounding mode
      * @see #setRoundingIncrement
      * @see #getRoundingIncrement
      * @see #setRoundingMode
      * @stable ICU 2.0
      */
     virtual ERoundingMode getRoundingMode(void) const override;
 
     /**
      * Set the rounding mode.
      * @param roundingMode A rounding mode
      * @see #setRoundingIncrement
      * @see #getRoundingIncrement
      * @see #getRoundingMode
      * @stable ICU 2.0
      */
     virtual void setRoundingMode(ERoundingMode roundingMode) override;
 
     /**
      * Get the width to which the output of format() is padded.
      * The width is counted in 16-bit code units.
      * @return the format width, or zero if no padding is in effect
      * @see #setFormatWidth
      * @see #getPadCharacterString
      * @see #setPadCharacter
      * @see #getPadPosition
      * @see #setPadPosition
      * @stable ICU 2.0
      */
     virtual int32_t getFormatWidth(void) const;
 
     /**
      * Set the width to which the output of format() is padded.
      * The width is counted in 16-bit code units.
      * This method also controls whether padding is enabled.
      * @param width the width to which to pad the result of
      * format(), or zero to disable padding.  A negative
      * width is equivalent to 0.
      * @see #getFormatWidth
      * @see #getPadCharacterString
      * @see #setPadCharacter
      * @see #getPadPosition
      * @see #setPadPosition
      * @stable ICU 2.0
      */
     virtual void setFormatWidth(int32_t width);
 
     /**
      * Get the pad character used to pad to the format width.  The
      * default is ' '.
      * @return a string containing the pad character. This will always
      * have a length of one 32-bit code point.
      * @see #setFormatWidth
      * @see #getFormatWidth
      * @see #setPadCharacter
      * @see #getPadPosition
      * @see #setPadPosition
      * @stable ICU 2.0
      */
     virtual UnicodeString getPadCharacterString() const;
 
     /**
      * Set the character used to pad to the format width.  If padding
      * is not enabled, then this will take effect if padding is later
      * enabled.
      * @param padChar a string containing the pad character. If the string
      * has length 0, then the pad character is set to ' '.  Otherwise
      * padChar.char32At(0) will be used as the pad character.
      * @see #setFormatWidth
      * @see #getFormatWidth
      * @see #getPadCharacterString
      * @see #getPadPosition
      * @see #setPadPosition
      * @stable ICU 2.0
      */
     virtual void setPadCharacter(const UnicodeString& padChar);
 
     /**
      * Get the position at which padding will take place.  This is the location
      * at which padding will be inserted if the result of format()
      * is shorter than the format width.
      * @return the pad position, one of kPadBeforePrefix,
      * kPadAfterPrefix, kPadBeforeSuffix, or
      * kPadAfterSuffix.
      * @see #setFormatWidth
      * @see #getFormatWidth
      * @see #setPadCharacter
      * @see #getPadCharacterString
      * @see #setPadPosition
      * @see #EPadPosition
      * @stable ICU 2.0
      */
     virtual EPadPosition getPadPosition(void) const;
 
     /**
      * Set the position at which padding will take place.  This is the location
      * at which padding will be inserted if the result of format()
      * is shorter than the format width.  This has no effect unless padding is
      * enabled.
      * @param padPos the pad position, one of kPadBeforePrefix,
      * kPadAfterPrefix, kPadBeforeSuffix, or
      * kPadAfterSuffix.
      * @see #setFormatWidth
      * @see #getFormatWidth
      * @see #setPadCharacter
      * @see #getPadCharacterString
      * @see #getPadPosition
      * @see #EPadPosition
      * @stable ICU 2.0
      */
     virtual void setPadPosition(EPadPosition padPos);
 
     /**
      * Return whether or not scientific notation is used.
      * @return true if this object formats and parses scientific notation
      * @see #setScientificNotation
      * @see #getMinimumExponentDigits
      * @see #setMinimumExponentDigits
      * @see #isExponentSignAlwaysShown
      * @see #setExponentSignAlwaysShown
      * @stable ICU 2.0
      */
     virtual UBool isScientificNotation(void) const;
 
     /**
      * Set whether or not scientific notation is used. When scientific notation
      * is used, the effective maximum number of integer digits is <= 8.  If the
      * maximum number of integer digits is set to more than 8, the effective
      * maximum will be 1.  This allows this call to generate a 'default' scientific
      * number format without additional changes.
      * @param useScientific true if this object formats and parses scientific
      * notation
      * @see #isScientificNotation
      * @see #getMinimumExponentDigits
      * @see #setMinimumExponentDigits
      * @see #isExponentSignAlwaysShown
      * @see #setExponentSignAlwaysShown
      * @stable ICU 2.0
      */
     virtual void setScientificNotation(UBool useScientific);
 
     /**
      * Return the minimum exponent digits that will be shown.
      * @return the minimum exponent digits that will be shown
      * @see #setScientificNotation
      * @see #isScientificNotation
      * @see #setMinimumExponentDigits
      * @see #isExponentSignAlwaysShown
      * @see #setExponentSignAlwaysShown
      * @stable ICU 2.0
      */
     virtual int8_t getMinimumExponentDigits(void) const;
 
     /**
      * Set the minimum exponent digits that will be shown.  This has no
      * effect unless scientific notation is in use.
      * @param minExpDig a value >= 1 indicating the fewest exponent digits
      * that will be shown.  Values less than 1 will be treated as 1.
      * @see #setScientificNotation
      * @see #isScientificNotation
      * @see #getMinimumExponentDigits
      * @see #isExponentSignAlwaysShown
      * @see #setExponentSignAlwaysShown
      * @stable ICU 2.0
      */
     virtual void setMinimumExponentDigits(int8_t minExpDig);
 
     /**
      * Return whether the exponent sign is always shown.
      * @return true if the exponent is always prefixed with either the
      * localized minus sign or the localized plus sign, false if only negative
      * exponents are prefixed with the localized minus sign.
      * @see #setScientificNotation
      * @see #isScientificNotation
      * @see #setMinimumExponentDigits
      * @see #getMinimumExponentDigits
      * @see #setExponentSignAlwaysShown
      * @stable ICU 2.0
      */
     virtual UBool isExponentSignAlwaysShown(void) const;
 
     /**
      * Set whether the exponent sign is always shown.  This has no effect
      * unless scientific notation is in use.
      * @param expSignAlways true if the exponent is always prefixed with either
      * the localized minus sign or the localized plus sign, false if only
      * negative exponents are prefixed with the localized minus sign.
      * @see #setScientificNotation
      * @see #isScientificNotation
      * @see #setMinimumExponentDigits
      * @see #getMinimumExponentDigits
      * @see #isExponentSignAlwaysShown
      * @stable ICU 2.0
      */
     virtual void setExponentSignAlwaysShown(UBool expSignAlways);
 
     /**
      * Return the grouping size. Grouping size is the number of digits between
      * grouping separators in the integer portion of a number.  For example,
      * in the number "123,456.78", the grouping size is 3.
      *
      * @return    the grouping size.
      * @see setGroupingSize
      * @see NumberFormat::isGroupingUsed
      * @see DecimalFormatSymbols::getGroupingSeparator
      * @stable ICU 2.0
      */
     int32_t getGroupingSize(void) const;
 
     /**
      * Set the grouping size. Grouping size is the number of digits between
      * grouping separators in the integer portion of a number.  For example,
      * in the number "123,456.78", the grouping size is 3.
      *
      * @param newValue    the new value of the grouping size.
      * @see getGroupingSize
      * @see NumberFormat::setGroupingUsed
      * @see DecimalFormatSymbols::setGroupingSeparator
      * @stable ICU 2.0
      */
     virtual void setGroupingSize(int32_t newValue);
 
     /**
      * Return the secondary grouping size. In some locales one
      * grouping interval is used for the least significant integer
      * digits (the primary grouping size), and another is used for all
      * others (the secondary grouping size).  A formatter supporting a
      * secondary grouping size will return a positive integer unequal
      * to the primary grouping size returned by
      * getGroupingSize().  For example, if the primary
      * grouping size is 4, and the secondary grouping size is 2, then
      * the number 123456789 formats as "1,23,45,6789", and the pattern
      * appears as "#,##,###0".
      * @return the secondary grouping size, or a value less than
      * one if there is none
      * @see setSecondaryGroupingSize
      * @see NumberFormat::isGroupingUsed
      * @see DecimalFormatSymbols::getGroupingSeparator
      * @stable ICU 2.4
      */
     int32_t getSecondaryGroupingSize(void) const;
 
     /**
      * Set the secondary grouping size. If set to a value less than 1,
      * then secondary grouping is turned off, and the primary grouping
      * size is used for all intervals, not just the least significant.
      *
      * @param newValue    the new value of the secondary grouping size.
      * @see getSecondaryGroupingSize
      * @see NumberFormat#setGroupingUsed
      * @see DecimalFormatSymbols::setGroupingSeparator
      * @stable ICU 2.4
      */
     virtual void setSecondaryGroupingSize(int32_t newValue);
 
     /**
      * Returns the minimum number of grouping digits.
      * Grouping separators are output if there are at least this many
      * digits to the left of the first (rightmost) grouping separator,
      * that is, there are at least (minimum grouping + grouping size) integer digits.
      * (Subject to isGroupingUsed().)
      *
      * For example, if this value is 2, and the grouping size is 3, then
      * 9999 -> "9999" and 10000 -> "10,000"
      *
      * The default value for this attribute is 0.
      * A value of 1, 0, or lower, means that the use of grouping separators
      * only depends on the grouping size (and on isGroupingUsed()).
      *
      * NOTE: The CLDR data is used in NumberFormatter but not in DecimalFormat.
      * This is for backwards compatibility reasons.
      *
      * For more control over grouping strategies, use NumberFormatter.
      *
      * @see setMinimumGroupingDigits
      * @see getGroupingSize
      * @stable ICU 64
      */
     int32_t getMinimumGroupingDigits() const;
 
     /**
      * Sets the minimum grouping digits. Setting the value to
      *  - 1: Turns off minimum grouping digits.
      *  - 0 or -1: The behavior is undefined.
      *  - UNUM_MINIMUM_GROUPING_DIGITS_AUTO: Display grouping using the default
      *      strategy for all locales.
      *  - UNUM_MINIMUM_GROUPING_DIGITS_MIN2: Display grouping using locale
      *      defaults, except do not show grouping on values smaller than 10000
      *      (such that there is a minimum of two digits before the first
      *      separator).
      *
      * For more control over grouping strategies, use NumberFormatter.
      *
      * @param newValue the new value of minimum grouping digits.
      * @see getMinimumGroupingDigits
      * @stable ICU 64
      */
     void setMinimumGroupingDigits(int32_t newValue);
 
     /**
      * Allows you to get the behavior of the decimal separator with integers.
      * (The decimal separator will always appear with decimals.)
      *
      * @return    true if the decimal separator always appear with decimals.
      * Example: Decimal ON: 12345 -> 12345.; OFF: 12345 -> 12345
      * @stable ICU 2.0
      */
     UBool isDecimalSeparatorAlwaysShown(void) const;
 
     /**
      * Allows you to set the behavior of the decimal separator with integers.
      * (The decimal separator will always appear with decimals.)
      *
      * @param newValue    set true if the decimal separator will always appear with decimals.
      * Example: Decimal ON: 12345 -> 12345.; OFF: 12345 -> 12345
      * @stable ICU 2.0
      */
     virtual void setDecimalSeparatorAlwaysShown(UBool newValue);
 
     /**
      * Allows you to get the parse behavior of the pattern decimal mark.
      *
      * @return    true if input must contain a match to decimal mark in pattern
      * @stable ICU 54
      */
     UBool isDecimalPatternMatchRequired(void) const;
 
     /**
      * Allows you to set the parse behavior of the pattern decimal mark.
      *
      * if true, the input must have a decimal mark if one was specified in the pattern. When
      * false the decimal mark may be omitted from the input.
      *
      * @param newValue    set true if input must contain a match to decimal mark in pattern
      * @stable ICU 54
      */
     virtual void setDecimalPatternMatchRequired(UBool newValue);
 
     /**
      * Returns whether to ignore exponents when parsing.
      *
      * @return Whether to ignore exponents when parsing.
      * @see #setParseNoExponent
      * @stable ICU 64
      */
     UBool isParseNoExponent() const;
 
     /**
      * Specifies whether to stop parsing when an exponent separator is encountered. For
      * example, parses "123E4" to 123 (with parse position 3) instead of 1230000 (with parse position
      * 5).
      *
      * @param value true to prevent exponents from being parsed; false to allow them to be parsed.
      * @stable ICU 64
      */
     void setParseNoExponent(UBool value);
 
     /**
      * Returns whether parsing is sensitive to case (lowercase/uppercase).
      *
      * @return Whether parsing is case-sensitive.
      * @see #setParseCaseSensitive
      * @stable ICU 64
      */
     UBool isParseCaseSensitive() const;
 
     /**
      * Whether to pay attention to case when parsing; default is to ignore case (perform
      * case-folding). For example, "A" == "a" in case-insensitive but not case-sensitive mode.
      *
      * Currency symbols are never case-folded. For example, "us$1.00" will not parse in case-insensitive
      * mode, even though "US$1.00" parses.
      *
      * @param value true to enable case-sensitive parsing (the default); false to force
      *              case-sensitive parsing behavior.
      * @stable ICU 64
      */
     void setParseCaseSensitive(UBool value);
 
     /**
      * Returns whether truncation of high-order integer digits should result in an error.
      * By default, setMaximumIntegerDigits truncates high-order digits silently.
      *
      * @return Whether an error code is set if high-order digits are truncated.
      * @see setFormatFailIfMoreThanMaxDigits
      * @stable ICU 64
      */
     UBool isFormatFailIfMoreThanMaxDigits() const;
 
     /**
      * Sets whether truncation of high-order integer digits should result in an error.
      * By default, setMaximumIntegerDigits truncates high-order digits silently.
      *
      * @param value Whether to set an error code if high-order digits are truncated.
      * @stable ICU 64
      */
     void setFormatFailIfMoreThanMaxDigits(UBool value);
 
     /**
      * Synthesizes a pattern string that represents the current state
      * of this Format object.
      *
      * @param result    Output param which will receive the pattern.
      *                  Previous contents are deleted.
      * @return          A reference to 'result'.
      * @see applyPattern
      * @stable ICU 2.0
      */
     virtual UnicodeString& toPattern(UnicodeString& result) const;
 
     /**
      * Synthesizes a localized pattern string that represents the current
      * state of this Format object.
      *
      * @param result    Output param which will receive the localized pattern.
      *                  Previous contents are deleted.
      * @return          A reference to 'result'.
      * @see applyPattern
      * @stable ICU 2.0
      */
     virtual UnicodeString& toLocalizedPattern(UnicodeString& result) const;
 
     /**
      * Apply the given pattern to this Format object.  A pattern is a
      * short-hand specification for the various formatting properties.
      * These properties can also be changed individually through the
      * various setter methods.
      * <P>
      * There is no limit to integer digits are set
      * by this routine, since that is the typical end-user desire;
      * use setMaximumInteger if you want to set a real value.
      * For negative numbers, use a second pattern, separated by a semicolon
      * <pre>
      * .      Example "#,#00.0#" -> 1,234.56
      * </pre>
      * This means a minimum of 2 integer digits, 1 fraction digit, and
      * a maximum of 2 fraction digits.
      * <pre>
      * .      Example: "#,#00.0#;(#,#00.0#)" for negatives in parentheses.
      * </pre>
      * In negative patterns, the minimum and maximum counts are ignored;
      * these are presumed to be set in the positive pattern.
      *
      * @param pattern    The pattern to be applied.
      * @param parseError Struct to receive information on position
      *                   of error if an error is encountered
      * @param status     Output param set to success/failure code on
      *                   exit. If the pattern is invalid, this will be
      *                   set to a failure result.
      * @stable ICU 2.0
      */
     virtual void applyPattern(const UnicodeString& pattern, UParseError& parseError, UErrorCode& status);
 
     /**
      * Sets the pattern.
      * @param pattern   The pattern to be applied.
      * @param status    Output param set to success/failure code on
      *                  exit. If the pattern is invalid, this will be
      *                  set to a failure result.
      * @stable ICU 2.0
      */
     virtual void applyPattern(const UnicodeString& pattern, UErrorCode& status);
 
     /**
      * Apply the given pattern to this Format object.  The pattern
      * is assumed to be in a localized notation. A pattern is a
      * short-hand specification for the various formatting properties.
      * These properties can also be changed individually through the
      * various setter methods.
      * <P>
      * There is no limit to integer digits are set
      * by this routine, since that is the typical end-user desire;
      * use setMaximumInteger if you want to set a real value.
      * For negative numbers, use a second pattern, separated by a semicolon
      * <pre>
      * .      Example "#,#00.0#" -> 1,234.56
      * </pre>
      * This means a minimum of 2 integer digits, 1 fraction digit, and
      * a maximum of 2 fraction digits.
      *
      * Example: "#,#00.0#;(#,#00.0#)" for negatives in parentheses.
      *
      * In negative patterns, the minimum and maximum counts are ignored;
      * these are presumed to be set in the positive pattern.
      *
      * @param pattern   The localized pattern to be applied.
      * @param parseError Struct to receive information on position
      *                   of error if an error is encountered
      * @param status    Output param set to success/failure code on
      *                  exit. If the pattern is invalid, this will be
      *                  set to a failure result.
      * @stable ICU 2.0
      */
     virtual void applyLocalizedPattern(const UnicodeString& pattern, UParseError& parseError,
                                        UErrorCode& status);
 
     /**
      * Apply the given pattern to this Format object.
      *
      * @param pattern   The localized pattern to be applied.
      * @param status    Output param set to success/failure code on
      *                  exit. If the pattern is invalid, this will be
      *                  set to a failure result.
      * @stable ICU 2.0
      */
     virtual void applyLocalizedPattern(const UnicodeString& pattern, UErrorCode& status);
 
 
     /**
      * Sets the maximum number of digits allowed in the integer portion of a
      * number. This override limits the integer digit count to 309.
      *
      * @param newValue    the new value of the maximum number of digits
      *                      allowed in the integer portion of a number.
      * @see NumberFormat#setMaximumIntegerDigits
      * @stable ICU 2.0
      */
     void setMaximumIntegerDigits(int32_t newValue) override;
 
     /**
      * Sets the minimum number of digits allowed in the integer portion of a
      * number. This override limits the integer digit count to 309.
      *
      * @param newValue    the new value of the minimum number of digits
      *                      allowed in the integer portion of a number.
      * @see NumberFormat#setMinimumIntegerDigits
      * @stable ICU 2.0
      */
     void setMinimumIntegerDigits(int32_t newValue) override;
 
     /**
      * Sets the maximum number of digits allowed in the fraction portion of a
      * number. This override limits the fraction digit count to 340.
      *
      * @param newValue    the new value of the maximum number of digits
      *                    allowed in the fraction portion of a number.
      * @see NumberFormat#setMaximumFractionDigits
      * @stable ICU 2.0
      */
     void setMaximumFractionDigits(int32_t newValue) override;
 
     /**
      * Sets the minimum number of digits allowed in the fraction portion of a
      * number. This override limits the fraction digit count to 340.
      *
      * @param newValue    the new value of the minimum number of digits
      *                    allowed in the fraction portion of a number.
      * @see NumberFormat#setMinimumFractionDigits
      * @stable ICU 2.0
      */
     void setMinimumFractionDigits(int32_t newValue) override;
 
     /**
      * Returns the minimum number of significant digits that will be
      * displayed. This value has no effect unless areSignificantDigitsUsed()
      * returns true.
      * @return the fewest significant digits that will be shown
      * @stable ICU 3.0
      */
     int32_t getMinimumSignificantDigits() const;
 
     /**
      * Returns the maximum number of significant digits that will be
      * displayed. This value has no effect unless areSignificantDigitsUsed()
      * returns true.
      * @return the most significant digits that will be shown
      * @stable ICU 3.0
      */
     int32_t getMaximumSignificantDigits() const;
 
     /**
      * Sets the minimum number of significant digits that will be
      * displayed.  If <code>min</code> is less than one then it is set
      * to one.  If the maximum significant digits count is less than
      * <code>min</code>, then it is set to <code>min</code>.
      * This function also enables the use of significant digits
      * by this formatter - areSignificantDigitsUsed() will return true.
      * @see #areSignificantDigitsUsed
      * @param min the fewest significant digits to be shown
      * @stable ICU 3.0
      */
     void setMinimumSignificantDigits(int32_t min);
 
     /**
      * Sets the maximum number of significant digits that will be
      * displayed.  If <code>max</code> is less than one then it is set
      * to one.  If the minimum significant digits count is greater
      * than <code>max</code>, then it is set to <code>max</code>.
      * This function also enables the use of significant digits
      * by this formatter - areSignificantDigitsUsed() will return true.
      * @see #areSignificantDigitsUsed
      * @param max the most significant digits to be shown
      * @stable ICU 3.0
      */
     void setMaximumSignificantDigits(int32_t max);
 
     /**
      * Returns true if significant digits are in use, or false if
      * integer and fraction digit counts are in use.
      * @return true if significant digits are in use
      * @stable ICU 3.0
      */
     UBool areSignificantDigitsUsed() const;
 
     /**
      * Sets whether significant digits are in use, or integer and
      * fraction digit counts are in use.
      * @param useSignificantDigits true to use significant digits, or
      * false to use integer and fraction digit counts
      * @stable ICU 3.0
      */
     void setSignificantDigitsUsed(UBool useSignificantDigits);
 
     /**
      * Sets the currency used to display currency
      * amounts.  This takes effect immediately, if this format is a
      * currency format.  If this format is not a currency format, then
      * the currency is used if and when this object becomes a
      * currency format through the application of a new pattern.
      * @param theCurrency a 3-letter ISO code indicating new currency
      * to use.  It need not be null-terminated.  May be the empty
      * string or nullptr to indicate no currency.
      * @param ec input-output error code
      * @stable ICU 3.0
      */
     void setCurrency(const char16_t* theCurrency, UErrorCode& ec) override;
 
 #ifndef U_FORCE_HIDE_DEPRECATED_API
     /**
      * Sets the currency used to display currency amounts.  See
      * setCurrency(const char16_t*, UErrorCode&).
      * @deprecated ICU 3.0. Use setCurrency(const char16_t*, UErrorCode&).
      */
     virtual void setCurrency(const char16_t* theCurrency);
 #endif  // U_FORCE_HIDE_DEPRECATED_API
 
     /**
      * Sets the `Currency Usage` object used to display currency.
      * This takes effect immediately, if this format is a
      * currency format.
      * @param newUsage new currency usage object to use.
      * @param ec input-output error code
      * @stable ICU 54
      */
     void setCurrencyUsage(UCurrencyUsage newUsage, UErrorCode* ec);
 
     /**
      * Returns the `Currency Usage` object used to display currency
      * @stable ICU 54
      */
     UCurrencyUsage getCurrencyUsage() const;
 
 #ifndef U_HIDE_INTERNAL_API
 
     /**
      *  Format a number and save it into the given DecimalQuantity.
      *  Internal, not intended for public use.
      *  @internal
      */
     void formatToDecimalQuantity(double number, number::impl::DecimalQuantity& output,
                                  UErrorCode& status) const;
 
     /**
      *  Get a DecimalQuantity corresponding to a formattable as it would be
      *  formatted by this DecimalFormat.
      *  Internal, not intended for public use.
      *  @internal
      */
     void formatToDecimalQuantity(const Formattable& number, number::impl::DecimalQuantity& output,
                                  UErrorCode& status) const;
 
 #endif  /* U_HIDE_INTERNAL_API */
 
     /**
      * Converts this DecimalFormat to a (Localized)NumberFormatter. Starting
      * in ICU 60, NumberFormatter is the recommended way to format numbers.
      * You can use the returned LocalizedNumberFormatter to format numbers and
      * get a FormattedNumber, which contains a string as well as additional
      * annotations about the formatted value.
      * 
      * If a memory allocation failure occurs, the return value of this method
      * might be null. If you are concerned about correct recovery from
      * out-of-memory situations, use this pattern:
      *
      * <pre>
      * FormattedNumber result;
      * if (auto* ptr = df->toNumberFormatter(status)) {
      *     result = ptr->formatDouble(123, status);
      * }
      * </pre>
      *
      * If you are not concerned about out-of-memory situations, or if your
      * environment throws exceptions when memory allocation failure occurs,
      * you can chain the methods, like this:
      *
      * <pre>
      * FormattedNumber result = df
      *     ->toNumberFormatter(status)
      *     ->formatDouble(123, status);
      * </pre>
      *
      * NOTE: The returned LocalizedNumberFormatter is owned by this DecimalFormat.
      * If a non-const method is called on the DecimalFormat, or if the DecimalFormat
      * is deleted, the object becomes invalid. If you plan to keep the return value
      * beyond the lifetime of the DecimalFormat, copy it to a local variable:
      *
      * <pre>
      * LocalizedNumberFormatter lnf;
      * if (auto* ptr = df->toNumberFormatter(status)) {
      *     lnf = *ptr;
      * }
      * </pre>
      *
      * @param status Set on failure, like U_MEMORY_ALLOCATION_ERROR.
      * @return A pointer to an internal object, or nullptr on failure.
      *         Do not delete the return value!
      * @stable ICU 64
      */
     const number::LocalizedNumberFormatter* toNumberFormatter(UErrorCode& status) const;
 
     /**
      * Return the class ID for this class.  This is useful only for
      * comparing to a return value from getDynamicClassID().  For example:
      * <pre>
      * .      Base* polymorphic_pointer = createPolymorphicObject();
      * .      if (polymorphic_pointer->getDynamicClassID() ==
      * .          Derived::getStaticClassID()) ...
      * </pre>
      * @return          The class ID for all objects of this class.
      * @stable ICU 2.0
      */
     static UClassID U_EXPORT2 getStaticClassID(void);
 
     /**
      * Returns a unique class ID POLYMORPHICALLY.  Pure virtual override.
      * This method is to implement a simple version of RTTI, since not all
      * C++ compilers support genuine RTTI.  Polymorphic operator==() and
      * clone() methods call this method.
      *
      * @return          The class ID for this object. All objects of a
      *                  given class have the same class ID.  Objects of
      *                  other classes have different class IDs.
      * @stable ICU 2.0
      */
     UClassID getDynamicClassID(void) const override;
 
   private:
 
     /** Rebuilds the formatter object from the property bag. */
     void touch(UErrorCode& status);
 
     /** Rebuilds the formatter object, ignoring any error code. */
     void touchNoError();
 
     /**
      * Updates the property bag with settings from the given pattern.
      *
      * @param pattern The pattern string to parse.
      * @param ignoreRounding Whether to leave out rounding information (minFrac, maxFrac, and rounding
      *     increment) when parsing the pattern. This may be desirable if a custom rounding mode, such
      *     as CurrencyUsage, is to be used instead. One of {@link
      *     PatternStringParser#IGNORE_ROUNDING_ALWAYS}, {@link PatternStringParser#IGNORE_ROUNDING_IF_CURRENCY},
      *     or {@link PatternStringParser#IGNORE_ROUNDING_NEVER}.
      * @see PatternAndPropertyUtils#parseToExistingProperties
      */
     void setPropertiesFromPattern(const UnicodeString& pattern, int32_t ignoreRounding,
                                   UErrorCode& status);
 
     const numparse::impl::NumberParserImpl* getParser(UErrorCode& status) const;
 
     const numparse::impl::NumberParserImpl* getCurrencyParser(UErrorCode& status) const;
 
     static void fieldPositionHelper(
         const number::impl::UFormattedNumberData& formatted,
         FieldPosition& fieldPosition,
         int32_t offset,
         UErrorCode& status);
 
     static void fieldPositionIteratorHelper(
         const number::impl::UFormattedNumberData& formatted,
         FieldPositionIterator* fpi,
         int32_t offset,
         UErrorCode& status);
 
     void setupFastFormat();
 
     bool fastFormatDouble(double input, UnicodeString& output) const;
 
     bool fastFormatInt64(int64_t input, UnicodeString& output) const;
 
     void doFastFormatInt32(int32_t input, bool isNegative, UnicodeString& output) const;
 
     //=====================================================================================//
     //                                   INSTANCE FIELDS                                   //
     //=====================================================================================//
 
 
     // One instance field for the implementation, keep all fields inside of an implementation
     // class defined in number_mapper.h
     number::impl::DecimalFormatFields* fields = nullptr;
 
     // Allow child class CompactDecimalFormat to access fProperties:
     friend class CompactDecimalFormat;
 
     // Allow MeasureFormat to use fieldPositionHelper:
     friend class MeasureFormat;
 
 };
 
 U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // _DECIMFMT
 //eof

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