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 // © 2017 and later: Unicode, Inc. and others.
 // License & terms of use: http://www.unicode.org/copyright.html
 
 #ifndef __NUMBERFORMATTER_H__
 #define __NUMBERFORMATTER_H__
 
 #include "unicode/utypes.h"
 
 #if U_SHOW_CPLUSPLUS_API
 
 #if !UCONFIG_NO_FORMATTING
 
 #include "unicode/appendable.h"
 #include "unicode/bytestream.h"
 #include "unicode/currunit.h"
 #include "unicode/dcfmtsym.h"
 #include "unicode/displayoptions.h"
 #include "unicode/fieldpos.h"
 #include "unicode/fpositer.h"
 #include "unicode/measunit.h"
 #include "unicode/nounit.h"
 #include "unicode/parseerr.h"
 #include "unicode/plurrule.h"
 #include "unicode/ucurr.h"
 #include "unicode/unum.h"
 #include "unicode/unumberformatter.h"
 #include "unicode/uobject.h"
 #include "unicode/unumberoptions.h"
 #include "unicode/formattednumber.h"
 
 /**
  * \file
  * \brief C++ API: All-in-one formatter for localized numbers, currencies, and units.
  * 
  * For a full list of options, see icu::number::NumberFormatterSettings.
  *
  * <pre>
  * // Most basic usage:
  * NumberFormatter::withLocale(...).format(123).toString();  // 1,234 in en-US
  *
  * // Custom notation, unit, and rounding precision:
  * NumberFormatter::with()
  *     .notation(Notation::compactShort())
  *     .unit(CurrencyUnit("EUR", status))
  *     .precision(Precision::maxDigits(2))
  *     .locale(...)
  *     .format(1234)
  *     .toString();  // €1.2K in en-US
  *
  * // Create a formatter in a singleton by value for use later:
  * static const LocalizedNumberFormatter formatter = NumberFormatter::withLocale(...)
  *     .unit(NoUnit::percent())
  *     .precision(Precision::fixedFraction(3));
  * formatter.format(5.9831).toString();  // 5.983% in en-US
  *
  * // Create a "template" in a singleton unique_ptr but without setting a locale until the call site:
  * std::unique_ptr<UnlocalizedNumberFormatter> template = NumberFormatter::with()
  *     .sign(UNumberSignDisplay::UNUM_SIGN_ALWAYS)
  *     .unit(MeasureUnit::getMeter())
  *     .unitWidth(UNumberUnitWidth::UNUM_UNIT_WIDTH_FULL_NAME)
  *     .clone();
  * template->locale(...).format(1234).toString();  // +1,234 meters in en-US
  * </pre>
  *
  * <p>
  * This API offers more features than DecimalFormat and is geared toward new users of ICU.
  *
  * <p>
  * NumberFormatter instances (i.e., LocalizedNumberFormatter and UnlocalizedNumberFormatter)
  * are immutable and thread safe. This means that invoking a configuration method has no
  * effect on the receiving instance; you must store and use the new number formatter instance it returns instead.
  *
  * <pre>
  * UnlocalizedNumberFormatter formatter = UnlocalizedNumberFormatter::with().notation(Notation::scientific());
  * formatter.precision(Precision.maxFraction(2)); // does nothing!
  * formatter.locale(Locale.getEnglish()).format(9.8765).toString(); // prints "9.8765E0", not "9.88E0"
  * </pre>
  *
  * <p>
  * This API is based on the <em>fluent</em> design pattern popularized by libraries such as Google's Guava. For
  * extensive details on the design of this API, read <a href="https://goo.gl/szi5VB">the design doc</a>.
  *
  * <p>
  * Note: To format monetary/currency values, specify the currency in the `.unit()` function.
  *
  * @author Shane Carr
  */
 
 U_NAMESPACE_BEGIN
 
 // Forward declarations:
 class IFixedDecimal;
 class FieldPositionIteratorHandler;
 class FormattedStringBuilder;
 
 namespace numparse {
 namespace impl {
 
 // Forward declarations:
 class NumberParserImpl;
 class MultiplierParseHandler;
 
 }
 }
 
 namespace units {
 
 // Forward declarations:
 class UnitsRouter;
 
 } // namespace units
 
 namespace number {  // icu::number
 
 // Forward declarations:
 class UnlocalizedNumberFormatter;
 class LocalizedNumberFormatter;
 class SimpleNumberFormatter;
 class FormattedNumber;
 class Notation;
 class ScientificNotation;
 class Precision;
 class FractionPrecision;
 class CurrencyPrecision;
 class IncrementPrecision;
 class IntegerWidth;
 
 namespace impl {
 
 // can't be #ifndef U_HIDE_INTERNAL_API; referenced throughout this file in public classes
 /**
  * Datatype for minimum/maximum fraction digits. Must be able to hold kMaxIntFracSig.
  *
  * @internal
  */
 typedef int16_t digits_t;
 
 // can't be #ifndef U_HIDE_INTERNAL_API; needed for struct initialization
 /**
  * Use a default threshold of 3. This means that the third time .format() is called, the data structures get built
  * using the "safe" code path. The first two calls to .format() will trigger the unsafe code path.
  *
  * @internal
  */
 static constexpr int32_t kInternalDefaultThreshold = 3;
 
 // Forward declarations:
 class Padder;
 struct MacroProps;
 struct MicroProps;
 class DecimalQuantity;
 class UFormattedNumberData;
 class NumberFormatterImpl;
 struct ParsedPatternInfo;
 class ScientificModifier;
 class MultiplierProducer;
 class RoundingImpl;
 class ScientificHandler;
 class Modifier;
 class AffixPatternProvider;
 class NumberPropertyMapper;
 struct DecimalFormatProperties;
 class MultiplierFormatHandler;
 class CurrencySymbols;
 class GeneratorHelpers;
 class DecNum;
 class NumberRangeFormatterImpl;
 struct RangeMacroProps;
 struct UFormattedNumberImpl;
 class MutablePatternModifier;
 class ImmutablePatternModifier;
 struct DecimalFormatWarehouse;
 struct SimpleMicroProps;
 class AdoptingSignumModifierStore;
 
 /**
  * Used for NumberRangeFormatter and implemented in numrange_fluent.cpp.
  * Declared here so it can be friended.
  *
  * @internal
  */
 void touchRangeLocales(impl::RangeMacroProps& macros);
 
 } // namespace impl
 
 /**
  * Extra name reserved in case it is needed in the future.
  *
  * @stable ICU 63
  */
 typedef Notation CompactNotation;
 
 /**
  * Extra name reserved in case it is needed in the future.
  *
  * @stable ICU 63
  */
 typedef Notation SimpleNotation;
 
 /**
  * A class that defines the notation style to be used when formatting numbers in NumberFormatter.
  *
  * @stable ICU 60
  */
 class U_I18N_API Notation : public UMemory {
   public:
     /**
      * Print the number using scientific notation (also known as scientific form, standard index form, or standard form
      * in the UK). The format for scientific notation varies by locale; for example, many Western locales display the
      * number in the form "#E0", where the number is displayed with one digit before the decimal separator, zero or more
      * digits after the decimal separator, and the corresponding power of 10 displayed after the "E".
      *
      * <p>
      * Example outputs in <em>en-US</em> when printing 8.765E4 through 8.765E-3:
      *
      * <pre>
      * 8.765E4
      * 8.765E3
      * 8.765E2
      * 8.765E1
      * 8.765E0
      * 8.765E-1
      * 8.765E-2
      * 8.765E-3
      * 0E0
      * </pre>
      *
      * @return A ScientificNotation for chaining or passing to the NumberFormatter notation() setter.
      * @stable ICU 60
      */
     static ScientificNotation scientific();
 
     /**
      * Print the number using engineering notation, a variant of scientific notation in which the exponent must be
      * divisible by 3.
      *
      * <p>
      * Example outputs in <em>en-US</em> when printing 8.765E4 through 8.765E-3:
      *
      * <pre>
      * 87.65E3
      * 8.765E3
      * 876.5E0
      * 87.65E0
      * 8.765E0
      * 876.5E-3
      * 87.65E-3
      * 8.765E-3
      * 0E0
      * </pre>
      *
      * @return A ScientificNotation for chaining or passing to the NumberFormatter notation() setter.
      * @stable ICU 60
      */
     static ScientificNotation engineering();
 
     /**
      * Print the number using short-form compact notation.
      *
      * <p>
      * <em>Compact notation</em>, defined in Unicode Technical Standard #35 Part 3 Section 2.4.1, prints numbers with
      * localized prefixes or suffixes corresponding to different powers of ten. Compact notation is similar to
      * engineering notation in how it scales numbers.
      *
      * <p>
      * Compact notation is ideal for displaying large numbers (over ~1000) to humans while at the same time minimizing
      * screen real estate.
      *
      * <p>
      * In short form, the powers of ten are abbreviated. In <em>en-US</em>, the abbreviations are "K" for thousands, "M"
      * for millions, "B" for billions, and "T" for trillions. Example outputs in <em>en-US</em> when printing 8.765E7
      * through 8.765E0:
      *
      * <pre>
      * 88M
      * 8.8M
      * 876K
      * 88K
      * 8.8K
      * 876
      * 88
      * 8.8
      * </pre>
      *
      * <p>
      * When compact notation is specified without an explicit rounding precision, numbers are rounded off to the closest
      * integer after scaling the number by the corresponding power of 10, but with a digit shown after the decimal
      * separator if there is only one digit before the decimal separator. The default compact notation rounding precision
      * is equivalent to:
      *
      * <pre>
      * Precision::integer().withMinDigits(2)
      * </pre>
      *
      * @return A CompactNotation for passing to the NumberFormatter notation() setter.
      * @stable ICU 60
      */
     static CompactNotation compactShort();
 
     /**
      * Print the number using long-form compact notation. For more information on compact notation, see
      * {@link #compactShort}.
      *
      * <p>
      * In long form, the powers of ten are spelled out fully. Example outputs in <em>en-US</em> when printing 8.765E7
      * through 8.765E0:
      *
      * <pre>
      * 88 million
      * 8.8 million
      * 876 thousand
      * 88 thousand
      * 8.8 thousand
      * 876
      * 88
      * 8.8
      * </pre>
      *
      * @return A CompactNotation for passing to the NumberFormatter notation() setter.
      * @stable ICU 60
      */
     static CompactNotation compactLong();
 
     /**
      * Print the number using simple notation without any scaling by powers of ten. This is the default behavior.
      *
      * <p>
      * Since this is the default behavior, this method needs to be called only when it is necessary to override a
      * previous setting.
      *
      * <p>
      * Example outputs in <em>en-US</em> when printing 8.765E7 through 8.765E0:
      *
      * <pre>
      * 87,650,000
      * 8,765,000
      * 876,500
      * 87,650
      * 8,765
      * 876.5
      * 87.65
      * 8.765
      * </pre>
      *
      * @return A SimpleNotation for passing to the NumberFormatter notation() setter.
      * @stable ICU 60
      */
     static SimpleNotation simple();
 
   private:
     enum NotationType {
         NTN_SCIENTIFIC, NTN_COMPACT, NTN_SIMPLE, NTN_ERROR
     } fType;
 
     union NotationUnion {
         // For NTN_SCIENTIFIC
         /** @internal (private) */
         struct ScientificSettings {
             /** @internal (private) */
             int8_t fEngineeringInterval;
             /** @internal (private) */
             bool fRequireMinInt;
             /** @internal (private) */
             impl::digits_t fMinExponentDigits;
             /** @internal (private) */
             UNumberSignDisplay fExponentSignDisplay;
         } scientific;
 
         // For NTN_COMPACT
         UNumberCompactStyle compactStyle;
 
         // For NTN_ERROR
         UErrorCode errorCode;
     } fUnion;
 
     typedef NotationUnion::ScientificSettings ScientificSettings;
 
     Notation(const NotationType &type, const NotationUnion &union_) : fType(type), fUnion(union_) {}
 
     Notation(UErrorCode errorCode) : fType(NTN_ERROR) {
         fUnion.errorCode = errorCode;
     }
 
     Notation() : fType(NTN_SIMPLE), fUnion() {}
 
     UBool copyErrorTo(UErrorCode &status) const {
         if (fType == NTN_ERROR) {
             status = fUnion.errorCode;
             return true;
         }
         return false;
     }
 
     // To allow MacroProps to initialize empty instances:
     friend struct impl::MacroProps;
     friend class ScientificNotation;
 
     // To allow implementation to access internal types:
     friend class impl::NumberFormatterImpl;
     friend class impl::ScientificModifier;
     friend class impl::ScientificHandler;
 
     // To allow access to the skeleton generation code:
     friend class impl::GeneratorHelpers;
 };
 
 /**
  * A class that defines the scientific notation style to be used when formatting numbers in NumberFormatter.
  *
  * <p>
  * To create a ScientificNotation, use one of the factory methods in {@link Notation}.
  *
  * @stable ICU 60
  */
 class U_I18N_API ScientificNotation : public Notation {
   public:
     /**
      * Sets the minimum number of digits to show in the exponent of scientific notation, padding with zeros if
      * necessary. Useful for fixed-width display.
      *
      * <p>
      * For example, with minExponentDigits=2, the number 123 will be printed as "1.23E02" in <em>en-US</em> instead of
      * the default "1.23E2".
      *
      * @param minExponentDigits
      *            The minimum number of digits to show in the exponent.
      * @return A ScientificNotation, for chaining.
      * @stable ICU 60
      */
     ScientificNotation withMinExponentDigits(int32_t minExponentDigits) const;
 
     /**
      * Sets whether to show the sign on positive and negative exponents in scientific notation. The default is AUTO,
      * showing the minus sign but not the plus sign.
      *
      * <p>
      * For example, with exponentSignDisplay=ALWAYS, the number 123 will be printed as "1.23E+2" in <em>en-US</em>
      * instead of the default "1.23E2".
      *
      * @param exponentSignDisplay
      *            The strategy for displaying the sign in the exponent.
      * @return A ScientificNotation, for chaining.
      * @stable ICU 60
      */
     ScientificNotation withExponentSignDisplay(UNumberSignDisplay exponentSignDisplay) const;
 
   private:
     // Inherit constructor
     using Notation::Notation;
 
     // Raw constructor for NumberPropertyMapper
     ScientificNotation(int8_t fEngineeringInterval, bool fRequireMinInt, impl::digits_t fMinExponentDigits,
                        UNumberSignDisplay fExponentSignDisplay);
 
     friend class Notation;
 
     // So that NumberPropertyMapper can create instances
     friend class impl::NumberPropertyMapper;
 };
 
 /**
  * Extra name reserved in case it is needed in the future.
  *
  * @stable ICU 63
  */
 typedef Precision SignificantDigitsPrecision;
 
 /**
  * A class that defines the rounding precision to be used when formatting numbers in NumberFormatter.
  *
  * <p>
  * To create a Precision, use one of the factory methods.
  *
  * @stable ICU 60
  */
 class U_I18N_API Precision : public UMemory {
 
   public:
     /**
      * Show all available digits to full precision.
      *
      * <p>
      * <strong>NOTE:</strong> When formatting a <em>double</em>, this method, along with {@link #minFraction} and
      * {@link #minSignificantDigits}, will trigger complex algorithm similar to <em>Dragon4</em> to determine the
      * low-order digits and the number of digits to display based on the value of the double.
      * If the number of fraction places or significant digits can be bounded, consider using {@link #maxFraction}
      * or {@link #maxSignificantDigits} instead to maximize performance.
      * For more information, read the following blog post.
      *
      * <p>
      * http://www.serpentine.com/blog/2011/06/29/here-be-dragons-advances-in-problems-you-didnt-even-know-you-had/
      *
      * @return A Precision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     static Precision unlimited();
 
     /**
      * Show numbers rounded if necessary to the nearest integer.
      *
      * @return A FractionPrecision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     static FractionPrecision integer();
 
     /**
      * Show numbers rounded if necessary to a certain number of fraction places (numerals after the decimal separator).
      * Additionally, pad with zeros to ensure that this number of places are always shown.
      *
      * <p>
      * Example output with minMaxFractionPlaces = 3:
      *
      * <p>
      * 87,650.000<br>
      * 8,765.000<br>
      * 876.500<br>
      * 87.650<br>
      * 8.765<br>
      * 0.876<br>
      * 0.088<br>
      * 0.009<br>
      * 0.000 (zero)
      *
      * <p>
      * This method is equivalent to {@link #minMaxFraction} with both arguments equal.
      *
      * @param minMaxFractionPlaces
      *            The minimum and maximum number of numerals to display after the decimal separator (rounding if too
      *            long or padding with zeros if too short).
      * @return A FractionPrecision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     static FractionPrecision fixedFraction(int32_t minMaxFractionPlaces);
 
     /**
      * Always show at least a certain number of fraction places after the decimal separator, padding with zeros if
      * necessary. Do not perform rounding (display numbers to their full precision).
      *
      * <p>
      * <strong>NOTE:</strong> If you are formatting <em>doubles</em>, see the performance note in {@link #unlimited}.
      *
      * @param minFractionPlaces
      *            The minimum number of numerals to display after the decimal separator (padding with zeros if
      *            necessary).
      * @return A FractionPrecision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     static FractionPrecision minFraction(int32_t minFractionPlaces);
 
     /**
      * Show numbers rounded if necessary to a certain number of fraction places (numerals after the decimal separator).
      * Unlike the other fraction rounding strategies, this strategy does <em>not</em> pad zeros to the end of the
      * number.
      *
      * @param maxFractionPlaces
      *            The maximum number of numerals to display after the decimal mark (rounding if necessary).
      * @return A FractionPrecision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     static FractionPrecision maxFraction(int32_t maxFractionPlaces);
 
     /**
      * Show numbers rounded if necessary to a certain number of fraction places (numerals after the decimal separator);
      * in addition, always show at least a certain number of places after the decimal separator, padding with zeros if
      * necessary.
      *
      * @param minFractionPlaces
      *            The minimum number of numerals to display after the decimal separator (padding with zeros if
      *            necessary).
      * @param maxFractionPlaces
      *            The maximum number of numerals to display after the decimal separator (rounding if necessary).
      * @return A FractionPrecision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     static FractionPrecision minMaxFraction(int32_t minFractionPlaces, int32_t maxFractionPlaces);
 
     /**
      * Show numbers rounded if necessary to a certain number of significant digits or significant figures. Additionally,
      * pad with zeros to ensure that this number of significant digits/figures are always shown.
      *
      * <p>
      * This method is equivalent to {@link #minMaxSignificantDigits} with both arguments equal.
      *
      * @param minMaxSignificantDigits
      *            The minimum and maximum number of significant digits to display (rounding if too long or padding with
      *            zeros if too short).
      * @return A precision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 62
      */
     static SignificantDigitsPrecision fixedSignificantDigits(int32_t minMaxSignificantDigits);
 
     /**
      * Always show at least a certain number of significant digits/figures, padding with zeros if necessary. Do not
      * perform rounding (display numbers to their full precision).
      *
      * <p>
      * <strong>NOTE:</strong> If you are formatting <em>doubles</em>, see the performance note in {@link #unlimited}.
      *
      * @param minSignificantDigits
      *            The minimum number of significant digits to display (padding with zeros if too short).
      * @return A precision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 62
      */
     static SignificantDigitsPrecision minSignificantDigits(int32_t minSignificantDigits);
 
     /**
      * Show numbers rounded if necessary to a certain number of significant digits/figures.
      *
      * @param maxSignificantDigits
      *            The maximum number of significant digits to display (rounding if too long).
      * @return A precision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 62
      */
     static SignificantDigitsPrecision maxSignificantDigits(int32_t maxSignificantDigits);
 
     /**
      * Show numbers rounded if necessary to a certain number of significant digits/figures; in addition, always show at
      * least a certain number of significant digits, padding with zeros if necessary.
      *
      * @param minSignificantDigits
      *            The minimum number of significant digits to display (padding with zeros if necessary).
      * @param maxSignificantDigits
      *            The maximum number of significant digits to display (rounding if necessary).
      * @return A precision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 62
      */
     static SignificantDigitsPrecision minMaxSignificantDigits(int32_t minSignificantDigits,
                                                               int32_t maxSignificantDigits);
 
     /**
      * Show numbers rounded if necessary to the closest multiple of a certain rounding increment. For example, if the
      * rounding increment is 0.5, then round 1.2 to 1 and round 1.3 to 1.5.
      *
      * <p>
      * In order to ensure that numbers are padded to the appropriate number of fraction places, call
      * withMinFraction() on the return value of this method.
      * For example, to round to the nearest 0.5 and always display 2 numerals after the
      * decimal separator (to display 1.2 as "1.00" and 1.3 as "1.50"), you can run:
      *
      * <pre>
      * Precision::increment(0.5).withMinFraction(2)
      * </pre>
      *
      * @param roundingIncrement
      *            The increment to which to round numbers.
      * @return A precision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     static IncrementPrecision increment(double roundingIncrement);
 
     /**
      * Version of `Precision::increment()` that takes an integer at a particular power of 10.
      *
      * To round to the nearest 0.5 and display 2 fraction digits, with this function, you should write one of the following:
      *
      * <pre>
      * Precision::incrementExact(5, -1).withMinFraction(2)
      * Precision::incrementExact(50, -2).withMinFraction(2)
      * Precision::incrementExact(50, -2)
      * </pre>
      *
      * This is analagous to ICU4J `Precision.increment(new BigDecimal("0.50"))`.
      *
      * This behavior is modeled after ECMA-402. For more information, see:
      * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/NumberFormat#roundingincrement
      *
      * @param mantissa
      *            The increment to which to round numbers.
      * @param magnitude
      *            The power of 10 of the ones digit of the mantissa.
      * @return A precision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 71
      */
     static IncrementPrecision incrementExact(uint64_t mantissa, int16_t magnitude);
 
     /**
      * Show numbers rounded and padded according to the rules for the currency unit. The most common
      * rounding precision settings for currencies include <code>Precision::fixedFraction(2)</code>,
      * <code>Precision::integer()</code>, and <code>Precision::increment(0.05)</code> for cash transactions
      * ("nickel rounding").
      *
      * <p>
      * The exact rounding details will be resolved at runtime based on the currency unit specified in the
      * NumberFormatter chain. To round according to the rules for one currency while displaying the symbol for another
      * currency, the withCurrency() method can be called on the return value of this method.
      *
      * @param currencyUsage
      *            Either STANDARD (for digital transactions) or CASH (for transactions where the rounding increment may
      *            be limited by the available denominations of cash or coins).
      * @return A CurrencyPrecision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     static CurrencyPrecision currency(UCurrencyUsage currencyUsage);
 
     /**
      * Configure how trailing zeros are displayed on numbers. For example, to hide trailing zeros
      * when the number is an integer, use UNUM_TRAILING_ZERO_HIDE_IF_WHOLE.
      *
      * @param trailingZeroDisplay Option to configure the display of trailing zeros.
      * @stable ICU 69
      */
     Precision trailingZeroDisplay(UNumberTrailingZeroDisplay trailingZeroDisplay) const;
 
   private:
     enum PrecisionType {
         RND_BOGUS,
         RND_NONE,
         RND_FRACTION,
         RND_SIGNIFICANT,
         RND_FRACTION_SIGNIFICANT,
 
         // Used for strange increments like 3.14.
         RND_INCREMENT,
 
         // Used for increments with 1 as the only digit. This is different than fraction
         // rounding because it supports having additional trailing zeros. For example, this
         // class is used to round with the increment 0.010.
         RND_INCREMENT_ONE,
 
         // Used for increments with 5 as the only digit (nickel rounding).
         RND_INCREMENT_FIVE,
 
         RND_CURRENCY,
         RND_ERROR
     } fType;
 
     union PrecisionUnion {
         /** @internal (private) */
         struct FractionSignificantSettings {
             // For RND_FRACTION, RND_SIGNIFICANT, and RND_FRACTION_SIGNIFICANT
             /** @internal (private) */
             impl::digits_t fMinFrac;
             /** @internal (private) */
             impl::digits_t fMaxFrac;
             /** @internal (private) */
             impl::digits_t fMinSig;
             /** @internal (private) */
             impl::digits_t fMaxSig;
             /** @internal (private) */
             UNumberRoundingPriority fPriority;
             /**
              * Whether to retain trailing zeros based on the looser strategy.
              * @internal (private)
              */
             bool fRetain;
         } fracSig;
         /** @internal (private) */
         struct IncrementSettings {
             // For RND_INCREMENT, RND_INCREMENT_ONE, and RND_INCREMENT_FIVE
             // Note: This is a union, so we shouldn't own memory, since
             // the default destructor would leak it.
             /** @internal (private) */
             uint64_t fIncrement;
             /** @internal (private) */
             impl::digits_t fIncrementMagnitude;
             /** @internal (private) */
             impl::digits_t fMinFrac;
         } increment;
         UCurrencyUsage currencyUsage; // For RND_CURRENCY
         UErrorCode errorCode; // For RND_ERROR
     } fUnion;
 
     UNumberTrailingZeroDisplay fTrailingZeroDisplay = UNUM_TRAILING_ZERO_AUTO;
 
     typedef PrecisionUnion::FractionSignificantSettings FractionSignificantSettings;
     typedef PrecisionUnion::IncrementSettings IncrementSettings;
 
     Precision(const PrecisionType& type, const PrecisionUnion& union_)
             : fType(type), fUnion(union_) {}
 
     Precision(UErrorCode errorCode) : fType(RND_ERROR) {
         fUnion.errorCode = errorCode;
     }
 
     Precision() : fType(RND_BOGUS) {}
 
     bool isBogus() const {
         return fType == RND_BOGUS;
     }
 
     UBool copyErrorTo(UErrorCode &status) const {
         if (fType == RND_ERROR) {
             status = fUnion.errorCode;
             return true;
         }
         return false;
     }
 
     // On the parent type so that this method can be called internally on Precision instances.
     Precision withCurrency(const CurrencyUnit &currency, UErrorCode &status) const;
 
     static FractionPrecision constructFraction(int32_t minFrac, int32_t maxFrac);
 
     static Precision constructSignificant(int32_t minSig, int32_t maxSig);
 
     static Precision constructFractionSignificant(
         const FractionPrecision &base,
         int32_t minSig,
         int32_t maxSig,
         UNumberRoundingPriority priority,
         bool retain);
 
     static IncrementPrecision constructIncrement(uint64_t increment, impl::digits_t magnitude);
 
     static CurrencyPrecision constructCurrency(UCurrencyUsage usage);
 
     // To allow MacroProps/MicroProps to initialize bogus instances:
     friend struct impl::MacroProps;
     friend struct impl::MicroProps;
 
     // To allow NumberFormatterImpl to access isBogus() and other internal methods:
     friend class impl::NumberFormatterImpl;
 
     // To allow NumberPropertyMapper to create instances from DecimalFormatProperties:
     friend class impl::NumberPropertyMapper;
 
     // To allow access to the main implementation class:
     friend class impl::RoundingImpl;
 
     // To allow child classes to call private methods:
     friend class FractionPrecision;
     friend class CurrencyPrecision;
     friend class IncrementPrecision;
 
     // To allow access to the skeleton generation code:
     friend class impl::GeneratorHelpers;
 
     // To allow access to isBogus and the default (bogus) constructor:
     friend class units::UnitsRouter;
 };
 
 /**
  * A class that defines a rounding precision based on a number of fraction places and optionally significant digits to be
  * used when formatting numbers in NumberFormatter.
  *
  * <p>
  * To create a FractionPrecision, use one of the factory methods on Precision.
  *
  * @stable ICU 60
  */
 class U_I18N_API FractionPrecision : public Precision {
   public:
     /**
      * Override maximum fraction digits with maximum significant digits depending on the magnitude
      * of the number. See UNumberRoundingPriority.
      *
      * @param minSignificantDigits
      *            Pad trailing zeros to achieve this minimum number of significant digits.
      * @param maxSignificantDigits
      *            Round the number to achieve this maximum number of significant digits.
      * @param priority
      *            How to disambiguate between fraction digits and significant digits.
      * @return A precision for chaining or passing to the NumberFormatter precision() setter.
      *
      * @stable ICU 69
      */
     Precision withSignificantDigits(
         int32_t minSignificantDigits,
         int32_t maxSignificantDigits,
         UNumberRoundingPriority priority) const;
 
     /**
      * Ensure that no less than this number of significant digits are retained when rounding
      * according to fraction rules.
      *
      * For example, with integer rounding, the number 3.141 becomes "3". However, with minimum
      * figures set to 2, 3.141 becomes "3.1" instead.
      *
      * This setting does not affect the number of trailing zeros. For example, 3.01 would print as
      * "3", not "3.0".
      *
      * This is equivalent to `withSignificantDigits(1, minSignificantDigits, RELAXED)`.
      *
      * @param minSignificantDigits
      *            The number of significant figures to guarantee.
      * @return A precision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     Precision withMinDigits(int32_t minSignificantDigits) const;
 
     /**
      * Ensure that no more than this number of significant digits are retained when rounding
      * according to fraction rules.
      *
      * For example, with integer rounding, the number 123.4 becomes "123". However, with maximum
      * figures set to 2, 123.4 becomes "120" instead.
      *
      * This setting does not affect the number of trailing zeros. For example, with fixed fraction
      * of 2, 123.4 would become "120.00".
      *
      * This is equivalent to `withSignificantDigits(1, maxSignificantDigits, STRICT)`.
      *
      * @param maxSignificantDigits
      *            Round the number to no more than this number of significant figures.
      * @return A precision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     Precision withMaxDigits(int32_t maxSignificantDigits) const;
 
   private:
     // Inherit constructor
     using Precision::Precision;
 
     // To allow parent class to call this class's constructor:
     friend class Precision;
 };
 
 /**
  * A class that defines a rounding precision parameterized by a currency to be used when formatting numbers in
  * NumberFormatter.
  *
  * <p>
  * To create a CurrencyPrecision, use one of the factory methods on Precision.
  *
  * @stable ICU 60
  */
 class U_I18N_API CurrencyPrecision : public Precision {
   public:
     /**
       * Associates a currency with this rounding precision.
       *
       * <p>
       * <strong>Calling this method is <em>not required</em></strong>, because the currency specified in unit()
       * is automatically applied to currency rounding precisions. However,
       * this method enables you to override that automatic association.
       *
       * <p>
       * This method also enables numbers to be formatted using currency rounding rules without explicitly using a
       * currency format.
       *
       * @param currency
       *            The currency to associate with this rounding precision.
       * @return A precision for chaining or passing to the NumberFormatter precision() setter.
       * @stable ICU 60
       */
     Precision withCurrency(const CurrencyUnit &currency) const;
 
   private:
     // Inherit constructor
     using Precision::Precision;
 
     // To allow parent class to call this class's constructor:
     friend class Precision;
 };
 
 /**
  * A class that defines a rounding precision parameterized by a rounding increment to be used when formatting numbers in
  * NumberFormatter.
  *
  * <p>
  * To create an IncrementPrecision, use one of the factory methods on Precision.
  *
  * @stable ICU 60
  */
 class U_I18N_API IncrementPrecision : public Precision {
   public:
     /**
      * Specifies the minimum number of fraction digits to render after the decimal separator, padding with zeros if
      * necessary.  By default, no trailing zeros are added.
      *
      * <p>
      * For example, if the rounding increment is 0.5 and minFrac is 2, then the resulting strings include "0.00",
      * "0.50", "1.00", and "1.50".
      *
      * <p>
      * Note: In ICU4J, this functionality is accomplished via the scale of the BigDecimal rounding increment.
      *
      * @param minFrac The minimum number of digits after the decimal separator.
      * @return A precision for chaining or passing to the NumberFormatter precision() setter.
      * @stable ICU 60
      */
     Precision withMinFraction(int32_t minFrac) const;
 
   private:
     // Inherit constructor
     using Precision::Precision;
 
     // To allow parent class to call this class's constructor:
     friend class Precision;
 };
 
 /**
  * A class that defines the strategy for padding and truncating integers before the decimal separator.
  *
  * <p>
  * To create an IntegerWidth, use one of the factory methods.
  *
  * @stable ICU 60
  * @see NumberFormatter
  */
 class U_I18N_API IntegerWidth : public UMemory {
   public:
     /**
      * Pad numbers at the beginning with zeros to guarantee a certain number of numerals before the decimal separator.
      *
      * <p>
      * For example, with minInt=3, the number 55 will get printed as "055".
      *
      * @param minInt
      *            The minimum number of places before the decimal separator.
      * @return An IntegerWidth for chaining or passing to the NumberFormatter integerWidth() setter.
      * @stable ICU 60
      */
     static IntegerWidth zeroFillTo(int32_t minInt);
 
     /**
      * Truncate numbers exceeding a certain number of numerals before the decimal separator.
      *
      * For example, with maxInt=3, the number 1234 will get printed as "234".
      *
      * @param maxInt
      *            The maximum number of places before the decimal separator. maxInt == -1 means no
      *            truncation.
      * @return An IntegerWidth for passing to the NumberFormatter integerWidth() setter.
      * @stable ICU 60
      */
     IntegerWidth truncateAt(int32_t maxInt);
 
   private:
     union {
         struct {
             impl::digits_t fMinInt;
             impl::digits_t fMaxInt;
             bool fFormatFailIfMoreThanMaxDigits;
         } minMaxInt;
         UErrorCode errorCode;
     } fUnion;
     bool fHasError = false;
 
     IntegerWidth(impl::digits_t minInt, impl::digits_t maxInt, bool formatFailIfMoreThanMaxDigits);
 
     IntegerWidth(UErrorCode errorCode) { // NOLINT
         fUnion.errorCode = errorCode;
         fHasError = true;
     }
 
     IntegerWidth() { // NOLINT
         fUnion.minMaxInt.fMinInt = -1;
     }
 
     /** Returns the default instance. */
     static IntegerWidth standard() {
         return IntegerWidth::zeroFillTo(1);
     }
 
     bool isBogus() const {
         return !fHasError && fUnion.minMaxInt.fMinInt == -1;
     }
 
     UBool copyErrorTo(UErrorCode &status) const {
         if (fHasError) {
             status = fUnion.errorCode;
             return true;
         }
         return false;
     }
 
     void apply(impl::DecimalQuantity &quantity, UErrorCode &status) const;
 
     bool operator==(const IntegerWidth& other) const;
 
     // To allow MacroProps/MicroProps to initialize empty instances:
     friend struct impl::MacroProps;
     friend struct impl::MicroProps;
 
     // To allow NumberFormatterImpl to access isBogus():
     friend class impl::NumberFormatterImpl;
 
     // To allow the use of this class when formatting:
     friend class impl::MutablePatternModifier;
     friend class impl::ImmutablePatternModifier;
 
     // So that NumberPropertyMapper can create instances
     friend class impl::NumberPropertyMapper;
 
     // To allow access to the skeleton generation code:
     friend class impl::GeneratorHelpers;
 };
 
 /**
  * A class that defines a quantity by which a number should be multiplied when formatting.
  *
  * <p>
  * To create a Scale, use one of the factory methods.
  *
  * @stable ICU 62
  */
 class U_I18N_API Scale : public UMemory {
   public:
     /**
      * Do not change the value of numbers when formatting or parsing.
      *
      * @return A Scale to prevent any multiplication.
      * @stable ICU 62
      */
     static Scale none();
 
     /**
      * Multiply numbers by a power of ten before formatting. Useful for combining with a percent unit:
      *
      * <pre>
      * NumberFormatter::with().unit(NoUnit::percent()).multiplier(Scale::powerOfTen(2))
      * </pre>
      *
      * @return A Scale for passing to the setter in NumberFormatter.
      * @stable ICU 62
      */
     static Scale powerOfTen(int32_t power);
 
     /**
      * Multiply numbers by an arbitrary value before formatting. Useful for unit conversions.
      *
      * This method takes a string in a decimal number format with syntax
      * as defined in the Decimal Arithmetic Specification, available at
      * http://speleotrove.com/decimal
      *
      * Also see the version of this method that takes a double.
      *
      * @return A Scale for passing to the setter in NumberFormatter.
      * @stable ICU 62
      */
     static Scale byDecimal(StringPiece multiplicand);
 
     /**
      * Multiply numbers by an arbitrary value before formatting. Useful for unit conversions.
      *
      * This method takes a double; also see the version of this method that takes an exact decimal.
      *
      * @return A Scale for passing to the setter in NumberFormatter.
      * @stable ICU 62
      */
     static Scale byDouble(double multiplicand);
 
     /**
      * Multiply a number by both a power of ten and by an arbitrary double value.
      *
      * @return A Scale for passing to the setter in NumberFormatter.
      * @stable ICU 62
      */
     static Scale byDoubleAndPowerOfTen(double multiplicand, int32_t power);
 
     // We need a custom destructor for the DecNum, which means we need to declare
     // the copy/move constructor/assignment quartet.
 
     /** @stable ICU 62 */
     Scale(const Scale& other);
 
     /** @stable ICU 62 */
     Scale& operator=(const Scale& other);
 
     /** @stable ICU 62 */
     Scale(Scale&& src) noexcept;
 
     /** @stable ICU 62 */
     Scale& operator=(Scale&& src) noexcept;
 
     /** @stable ICU 62 */
     ~Scale();
 
 #ifndef U_HIDE_INTERNAL_API
     /** @internal */
     Scale(int32_t magnitude, impl::DecNum* arbitraryToAdopt);
 #endif  /* U_HIDE_INTERNAL_API */
 
   private:
     int32_t fMagnitude;
     impl::DecNum* fArbitrary;
     UErrorCode fError;
 
     Scale(UErrorCode error) : fMagnitude(0), fArbitrary(nullptr), fError(error) {}
 
     Scale() : fMagnitude(0), fArbitrary(nullptr), fError(U_ZERO_ERROR) {}
 
     bool isValid() const {
         return fMagnitude != 0 || fArbitrary != nullptr;
     }
 
     UBool copyErrorTo(UErrorCode &status) const {
         if (U_FAILURE(fError)) {
             status = fError;
             return true;
         }
         return false;
     }
 
     void applyTo(impl::DecimalQuantity& quantity) const;
 
     void applyReciprocalTo(impl::DecimalQuantity& quantity) const;
 
     // To allow MacroProps/MicroProps to initialize empty instances:
     friend struct impl::MacroProps;
     friend struct impl::MicroProps;
 
     // To allow NumberFormatterImpl to access isBogus() and perform other operations:
     friend class impl::NumberFormatterImpl;
 
     // To allow the helper class MultiplierFormatHandler access to private fields:
     friend class impl::MultiplierFormatHandler;
 
     // To allow access to the skeleton generation code:
     friend class impl::GeneratorHelpers;
 
     // To allow access to parsing code:
     friend class ::icu::numparse::impl::NumberParserImpl;
     friend class ::icu::numparse::impl::MultiplierParseHandler;
 };
 
 namespace impl {
 
 // Do not enclose entire StringProp with #ifndef U_HIDE_INTERNAL_API, needed for a protected field.
 // And do not enclose its class boilerplate within #ifndef U_HIDE_INTERNAL_API.
 /**
  * Manages NumberFormatterSettings::usage()'s char* instance on the heap.
  * @internal
  */
 class U_I18N_API StringProp : public UMemory {
 
   public:
     /** @internal */
     ~StringProp();
 
     /** @internal */
     StringProp(const StringProp &other);
 
     /** @internal */
     StringProp &operator=(const StringProp &other);
 
 #ifndef U_HIDE_INTERNAL_API
 
     /** @internal */
     StringProp(StringProp &&src) noexcept;
 
     /** @internal */
     StringProp &operator=(StringProp &&src) noexcept;
 
     /** @internal */
     int16_t length() const {
         return fLength;
     }
 
     /** @internal
      * Makes a copy of value. Set to "" to unset.
      */
     void set(StringPiece value);
 
     /** @internal */
     bool isSet() const {
         return fLength > 0;
     }
 
 #endif // U_HIDE_INTERNAL_API
 
   private:
     char *fValue;
     int16_t fLength;
     UErrorCode fError;
 
     StringProp() : fValue(nullptr), fLength(0), fError(U_ZERO_ERROR) {
     }
 
     /** @internal (private) */
     UBool copyErrorTo(UErrorCode &status) const {
         if (U_FAILURE(fError)) {
             status = fError;
             return true;
         }
         return false;
     }
 
     // Allow NumberFormatterImpl to access fValue.
     friend class impl::NumberFormatterImpl;
 
     // Allow skeleton generation code to access private members.
     friend class impl::GeneratorHelpers;
 
     // Allow MacroProps/MicroProps to initialize empty instances and to call
     // copyErrorTo().
     friend struct impl::MacroProps;
 };
 
 // Do not enclose entire SymbolsWrapper with #ifndef U_HIDE_INTERNAL_API, needed for a protected field
 /** @internal */
 class U_I18N_API SymbolsWrapper : public UMemory {
   public:
     /** @internal */
     SymbolsWrapper() : fType(SYMPTR_NONE), fPtr{nullptr} {}
 
     /** @internal */
     SymbolsWrapper(const SymbolsWrapper &other);
 
     /** @internal */
     SymbolsWrapper &operator=(const SymbolsWrapper &other);
 
     /** @internal */
     SymbolsWrapper(SymbolsWrapper&& src) noexcept;
 
     /** @internal */
     SymbolsWrapper &operator=(SymbolsWrapper&& src) noexcept;
 
     /** @internal */
     ~SymbolsWrapper();
 
 #ifndef U_HIDE_INTERNAL_API
 
     /**
      * The provided object is copied, but we do not adopt it.
      * @internal
      */
     void setTo(const DecimalFormatSymbols &dfs);
 
     /**
      * Adopt the provided object.
      * @internal
      */
     void setTo(const NumberingSystem *ns);
 
     /**
      * Whether the object is currently holding a DecimalFormatSymbols.
      * @internal
      */
     bool isDecimalFormatSymbols() const;
 
     /**
      * Whether the object is currently holding a NumberingSystem.
      * @internal
      */
     bool isNumberingSystem() const;
 
     /**
      * Get the DecimalFormatSymbols pointer. No ownership change.
      * @internal
      */
     const DecimalFormatSymbols *getDecimalFormatSymbols() const;
 
     /**
      * Get the NumberingSystem pointer. No ownership change.
      * @internal
      */
     const NumberingSystem *getNumberingSystem() const;
 
 #endif  // U_HIDE_INTERNAL_API
 
     /** @internal */
     UBool copyErrorTo(UErrorCode &status) const {
         if (fType == SYMPTR_DFS && fPtr.dfs == nullptr) {
             status = U_MEMORY_ALLOCATION_ERROR;
             return true;
         } else if (fType == SYMPTR_NS && fPtr.ns == nullptr) {
             status = U_MEMORY_ALLOCATION_ERROR;
             return true;
         }
         return false;
     }
 
   private:
     enum SymbolsPointerType {
         SYMPTR_NONE, SYMPTR_DFS, SYMPTR_NS
     } fType;
 
     union {
         const DecimalFormatSymbols *dfs;
         const NumberingSystem *ns;
     } fPtr;
 
     void doCopyFrom(const SymbolsWrapper &other);
 
     void doMoveFrom(SymbolsWrapper&& src);
 
     void doCleanup();
 };
 
 // Do not enclose entire Grouper with #ifndef U_HIDE_INTERNAL_API, needed for a protected field
 /** @internal */
 class U_I18N_API Grouper : public UMemory {
   public:
 #ifndef U_HIDE_INTERNAL_API
     /** @internal */
     static Grouper forStrategy(UNumberGroupingStrategy grouping);
 
     /**
      * Resolve the values in Properties to a Grouper object.
      * @internal
      */
     static Grouper forProperties(const DecimalFormatProperties& properties);
 
     // Future: static Grouper forProperties(DecimalFormatProperties& properties);
 
     /** @internal */
     Grouper(int16_t grouping1, int16_t grouping2, int16_t minGrouping, UNumberGroupingStrategy strategy)
             : fGrouping1(grouping1),
               fGrouping2(grouping2),
               fMinGrouping(minGrouping),
               fStrategy(strategy) {}
 
     /** @internal */
     int16_t getPrimary() const;
 
     /** @internal */
     int16_t getSecondary() const;
 #endif  // U_HIDE_INTERNAL_API
 
   private:
     /**
      * The grouping sizes, with the following special values:
      * <ul>
      * <li>-1 = no grouping
      * <li>-2 = needs locale data
      * <li>-4 = fall back to Western grouping if not in locale
      * </ul>
      */
     int16_t fGrouping1;
     int16_t fGrouping2;
 
     /**
      * The minimum grouping size, with the following special values:
      * <ul>
      * <li>-2 = needs locale data
      * <li>-3 = no less than 2
      * </ul>
      */
     int16_t fMinGrouping;
 
     /**
      * The UNumberGroupingStrategy that was used to create this Grouper, or UNUM_GROUPING_COUNT if this
      * was not created from a UNumberGroupingStrategy.
      */
     UNumberGroupingStrategy fStrategy;
 
     Grouper() : fGrouping1(-3) {}
 
     bool isBogus() const {
         return fGrouping1 == -3;
     }
 
     /** NON-CONST: mutates the current instance. */
     void setLocaleData(const impl::ParsedPatternInfo &patternInfo, const Locale& locale);
 
     bool groupAtPosition(int32_t position, const impl::DecimalQuantity &value) const;
 
     // To allow MacroProps/MicroProps to initialize empty instances:
     friend struct MacroProps;
     friend struct MicroProps;
     friend struct SimpleMicroProps;
 
     // To allow NumberFormatterImpl to access isBogus() and perform other operations:
     friend class NumberFormatterImpl;
     friend class ::icu::number::SimpleNumberFormatter;
 
     // To allow NumberParserImpl to perform setLocaleData():
     friend class ::icu::numparse::impl::NumberParserImpl;
 
     // To allow access to the skeleton generation code:
     friend class impl::GeneratorHelpers;
 };
 
 // Do not enclose entire Padder with #ifndef U_HIDE_INTERNAL_API, needed for a protected field
 /** @internal */
 class U_I18N_API Padder : public UMemory {
   public:
 #ifndef U_HIDE_INTERNAL_API
     /** @internal */
     static Padder none();
 
     /** @internal */
     static Padder codePoints(UChar32 cp, int32_t targetWidth, UNumberFormatPadPosition position);
 
     /** @internal */
     static Padder forProperties(const DecimalFormatProperties& properties);
 #endif  // U_HIDE_INTERNAL_API
 
   private:
     UChar32 fWidth;  // -3 = error; -2 = bogus; -1 = no padding
     union {
         struct {
             int32_t fCp;
             UNumberFormatPadPosition fPosition;
         } padding;
         UErrorCode errorCode;
     } fUnion;
 
     Padder(UChar32 cp, int32_t width, UNumberFormatPadPosition position);
 
     Padder(int32_t width);
 
     Padder(UErrorCode errorCode) : fWidth(-3) { // NOLINT
         fUnion.errorCode = errorCode;
     }
 
     Padder() : fWidth(-2) {} // NOLINT
 
     bool isBogus() const {
         return fWidth == -2;
     }
 
     UBool copyErrorTo(UErrorCode &status) const {
         if (fWidth == -3) {
             status = fUnion.errorCode;
             return true;
         }
         return false;
     }
 
     bool isValid() const {
         return fWidth > 0;
     }
 
     int32_t padAndApply(const impl::Modifier &mod1, const impl::Modifier &mod2,
                         FormattedStringBuilder &string, int32_t leftIndex, int32_t rightIndex,
                         UErrorCode &status) const;
 
     // To allow MacroProps/MicroProps to initialize empty instances:
     friend struct MacroProps;
     friend struct MicroProps;
 
     // To allow NumberFormatterImpl to access isBogus() and perform other operations:
     friend class impl::NumberFormatterImpl;
 
     // To allow access to the skeleton generation code:
     friend class impl::GeneratorHelpers;
 };
 
 // Do not enclose entire MacroProps with #ifndef U_HIDE_INTERNAL_API, needed for a protected field
 /** @internal */
 struct U_I18N_API MacroProps : public UMemory {
     /** @internal */
     Notation notation;
 
     /** @internal */
     MeasureUnit unit;  // = MeasureUnit();  (the base dimensionless unit)
 
     /** @internal */
     MeasureUnit perUnit;  // = MeasureUnit();  (the base dimensionless unit)
 
     /** @internal */
     Precision precision;  // = Precision();  (bogus)
 
     /** @internal */
     UNumberFormatRoundingMode roundingMode = UNUM_ROUND_HALFEVEN;
 
     /** @internal */
     Grouper grouper;  // = Grouper();  (bogus)
 
     /** @internal */
     Padder padder;    // = Padder();   (bogus)
 
     /** @internal */
     IntegerWidth integerWidth; // = IntegerWidth(); (bogus)
 
     /** @internal */
     SymbolsWrapper symbols;
 
     // UNUM_XYZ_COUNT denotes null (bogus) values.
 
     /** @internal */
     UNumberUnitWidth unitWidth = UNUM_UNIT_WIDTH_COUNT;
 
     /** @internal */
     UNumberSignDisplay sign = UNUM_SIGN_COUNT;
 
     /** @internal */
     bool approximately = false;
 
     /** @internal */
     UNumberDecimalSeparatorDisplay decimal = UNUM_DECIMAL_SEPARATOR_COUNT;
 
     /** @internal */
     Scale scale;  // = Scale();  (benign value)
 
     /** @internal */
     StringProp usage;  // = StringProp();  (no usage)
 
     /** @internal */
     StringProp unitDisplayCase;  // = StringProp();  (nominative)
 
     /** @internal */
     const AffixPatternProvider* affixProvider = nullptr;  // no ownership
 
     /** @internal */
     const PluralRules* rules = nullptr;  // no ownership
 
     /** @internal */
     int32_t threshold = kInternalDefaultThreshold;
 
     /** @internal */
     Locale locale;
 
     // NOTE: Uses default copy and move constructors.
 
     /**
      * Check all members for errors.
      * @internal
      */
     bool copyErrorTo(UErrorCode &status) const {
         return notation.copyErrorTo(status) || precision.copyErrorTo(status) ||
                padder.copyErrorTo(status) || integerWidth.copyErrorTo(status) ||
                symbols.copyErrorTo(status) || scale.copyErrorTo(status) || usage.copyErrorTo(status) ||
                unitDisplayCase.copyErrorTo(status);
     }
 };
 
 } // namespace impl
 
 #if (U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN) && defined(_MSC_VER)
 // Ignore MSVC warning 4661. This is generated for NumberFormatterSettings<>::toSkeleton() as this method
 // is defined elsewhere (in number_skeletons.cpp). The compiler is warning that the explicit template instantiation
 // inside this single translation unit (CPP file) is incomplete, and thus it isn't sure if the template class is
 // fully defined. However, since each translation unit explicitly instantiates all the necessary template classes,
 // they will all be passed to the linker, and the linker will still find and export all the class members.
 #pragma warning(push)
 #pragma warning(disable: 4661)
 #endif
 
 /**
  * An abstract base class for specifying settings related to number formatting. This class is implemented by
  * {@link UnlocalizedNumberFormatter} and {@link LocalizedNumberFormatter}. This class is not intended for
  * public subclassing.
  */
 template<typename Derived>
 class U_I18N_API NumberFormatterSettings {
   public:
     /**
      * Specifies the notation style (simple, scientific, or compact) for rendering numbers.
      *
      * <ul>
      * <li>Simple notation: "12,300"
      * <li>Scientific notation: "1.23E4"
      * <li>Compact notation: "12K"
      * </ul>
      *
      * <p>
      * All notation styles will be properly localized with locale data, and all notation styles are compatible with
      * units, rounding precisions, and other number formatter settings.
      *
      * <p>
      * Pass this method the return value of a {@link Notation} factory method. For example:
      *
      * <pre>
      * NumberFormatter::with().notation(Notation::compactShort())
      * </pre>
      *
      * The default is to use simple notation.
      *
      * @param notation
      *            The notation strategy to use.
      * @return The fluent chain.
      * @see Notation
      * @stable ICU 60
      */
     Derived notation(const Notation &notation) const &;
 
     /**
      * Overload of notation() for use on an rvalue reference.
      *
      * @param notation
      *            The notation strategy to use.
      * @return The fluent chain.
      * @see #notation
      * @stable ICU 62
      */
     Derived notation(const Notation &notation) &&;
 
     /**
      * Specifies the unit (unit of measure, currency, or percent) to associate with rendered numbers.
      *
      * <ul>
      * <li>Unit of measure: "12.3 meters"
      * <li>Currency: "$12.30"
      * <li>Percent: "12.3%"
      * </ul>
      *
      * All units will be properly localized with locale data, and all units are compatible with notation styles,
      * rounding precisions, and other number formatter settings.
      *
      * \note If the usage() is set, the output unit **will be changed** to
      *       produce localised units, according to usage, locale and unit. See
      *       FormattedNumber::getOutputUnit().
      *
      * Pass this method any instance of {@link MeasureUnit}. For units of measure:
      *
      * <pre>
      * NumberFormatter::with().unit(MeasureUnit::getMeter())
      * NumberFormatter::with().unit(MeasureUnit::forIdentifier("foot-per-second", status))
      * </pre>
      *
      * Currency:
      *
      * <pre>
      * NumberFormatter::with().unit(CurrencyUnit(u"USD", status))
      * </pre>
      *
      * Percent:
      *
      * <pre>
      * NumberFormatter::with().unit(NoUnit.percent())
      * </pre>
      *
      * See {@link #perUnit} for information on how to format strings like "5 meters per second".
      *
      * The default is to render without units (equivalent to NoUnit.base()).
      *
      * @param unit
      *            The unit to render.
      * @return The fluent chain.
      * @see MeasureUnit
      * @see Currency
      * @see NoUnit
      * @see #perUnit
      * @stable ICU 60
      */
     Derived unit(const icu::MeasureUnit &unit) const &;
 
     /**
      * Overload of unit() for use on an rvalue reference.
      *
      * @param unit
      *            The unit to render.
      * @return The fluent chain.
      * @see #unit
      * @stable ICU 62
      */
     Derived unit(const icu::MeasureUnit &unit) &&;
 
     /**
      * Like unit(), but takes ownership of a pointer.  Convenient for use with the MeasureFormat factory
      * methods that return pointers that need ownership.
      *
      * Note: consider using the MeasureFormat factory methods that return by value.
      *
      * @param unit
      *            The unit to render.
      * @return The fluent chain.
      * @see #unit
      * @see MeasureUnit
      * @stable ICU 60
      */
     Derived adoptUnit(icu::MeasureUnit *unit) const &;
 
     /**
      * Overload of adoptUnit() for use on an rvalue reference.
      *
      * @param unit
      *            The unit to render.
      * @return The fluent chain.
      * @see #adoptUnit
      * @stable ICU 62
      */
     Derived adoptUnit(icu::MeasureUnit *unit) &&;
 
     /**
      * Sets a unit to be used in the denominator. For example, to format "3 m/s", pass METER to the unit and SECOND to
      * the perUnit.
      *
      * Pass this method any instance of {@link MeasureUnit}. Example:
      *
      * <pre>
      * NumberFormatter::with()
      *      .unit(MeasureUnit::getMeter())
      *      .perUnit(MeasureUnit::getSecond())
      * </pre>
      *
      * The default is not to display any unit in the denominator.
      *
      * If a per-unit is specified without a primary unit via {@link #unit}, the behavior is undefined.
      *
      * @param perUnit
      *            The unit to render in the denominator.
      * @return The fluent chain
      * @see #unit
      * @stable ICU 61
      */
     Derived perUnit(const icu::MeasureUnit &perUnit) const &;
 
     /**
      * Overload of perUnit() for use on an rvalue reference.
      *
      * @param perUnit
      *            The unit to render in the denominator.
      * @return The fluent chain.
      * @see #perUnit
      * @stable ICU 62
      */
     Derived perUnit(const icu::MeasureUnit &perUnit) &&;
 
     /**
      * Like perUnit(), but takes ownership of a pointer.  Convenient for use with the MeasureFormat factory
      * methods that return pointers that need ownership.
      *
      * Note: consider using the MeasureFormat factory methods that return by value.
      *
      * @param perUnit
      *            The unit to render in the denominator.
      * @return The fluent chain.
      * @see #perUnit
      * @see MeasureUnit
      * @stable ICU 61
      */
     Derived adoptPerUnit(icu::MeasureUnit *perUnit) const &;
 
     /**
      * Overload of adoptPerUnit() for use on an rvalue reference.
      *
      * @param perUnit
      *            The unit to render in the denominator.
      * @return The fluent chain.
      * @see #adoptPerUnit
      * @stable ICU 62
      */
     Derived adoptPerUnit(icu::MeasureUnit *perUnit) &&;
 
     /**
      * Specifies the rounding precision to use when formatting numbers.
      *
      * <ul>
      * <li>Round to 3 decimal places: "3.142"
      * <li>Round to 3 significant figures: "3.14"
      * <li>Round to the closest nickel: "3.15"
      * <li>Do not perform rounding: "3.1415926..."
      * </ul>
      *
      * <p>
      * Pass this method the return value of one of the factory methods on {@link Precision}. For example:
      *
      * <pre>
      * NumberFormatter::with().precision(Precision::fixedFraction(2))
      * </pre>
      *
      * <p>
      * In most cases, the default rounding strategy is to round to 6 fraction places; i.e.,
      * <code>Precision.maxFraction(6)</code>. The exceptions are if compact notation is being used, then the compact
      * notation rounding strategy is used (see {@link Notation#compactShort} for details), or if the unit is a currency,
      * then standard currency rounding is used, which varies from currency to currency (see {@link Precision#currency} for
      * details).
      *
      * @param precision
      *            The rounding precision to use.
      * @return The fluent chain.
      * @see Precision
      * @stable ICU 62
      */
     Derived precision(const Precision& precision) const &;
 
     /**
      * Overload of precision() for use on an rvalue reference.
      *
      * @param precision
      *            The rounding precision to use.
      * @return The fluent chain.
      * @see #precision
      * @stable ICU 62
      */
     Derived precision(const Precision& precision) &&;
 
     /**
      * Specifies how to determine the direction to round a number when it has more digits than fit in the
      * desired precision.  When formatting 1.235:
      *
      * <ul>
      * <li>Ceiling rounding mode with integer precision: "2"
      * <li>Half-down rounding mode with 2 fixed fraction digits: "1.23"
      * <li>Half-up rounding mode with 2 fixed fraction digits: "1.24"
      * </ul>
      *
      * The default is HALF_EVEN. For more information on rounding mode, see the ICU userguide here:
      *
      * https://unicode-org.github.io/icu/userguide/format_parse/numbers/rounding-modes
      *
      * @param roundingMode The rounding mode to use.
      * @return The fluent chain.
      * @stable ICU 62
      */
     Derived roundingMode(UNumberFormatRoundingMode roundingMode) const &;
 
     /**
      * Overload of roundingMode() for use on an rvalue reference.
      *
      * @param roundingMode The rounding mode to use.
      * @return The fluent chain.
      * @see #roundingMode
      * @stable ICU 62
      */
     Derived roundingMode(UNumberFormatRoundingMode roundingMode) &&;
 
     /**
      * Specifies the grouping strategy to use when formatting numbers.
      *
      * <ul>
      * <li>Default grouping: "12,300" and "1,230"
      * <li>Grouping with at least 2 digits: "12,300" and "1230"
      * <li>No grouping: "12300" and "1230"
      * </ul>
      *
      * <p>
      * The exact grouping widths will be chosen based on the locale.
      *
      * <p>
      * Pass this method an element from the {@link UNumberGroupingStrategy} enum. For example:
      *
      * <pre>
      * NumberFormatter::with().grouping(UNUM_GROUPING_MIN2)
      * </pre>
      *
      * The default is to perform grouping according to locale data; most locales, but not all locales,
      * enable it by default.
      *
      * @param strategy
      *            The grouping strategy to use.
      * @return The fluent chain.
      * @stable ICU 61
      */
     Derived grouping(UNumberGroupingStrategy strategy) const &;
 
     /**
      * Overload of grouping() for use on an rvalue reference.
      *
      * @param strategy
      *            The grouping strategy to use.
      * @return The fluent chain.
      * @see #grouping
      * @stable ICU 62
      */
     Derived grouping(UNumberGroupingStrategy strategy) &&;
 
     /**
      * Specifies the minimum and maximum number of digits to render before the decimal mark.
      *
      * <ul>
      * <li>Zero minimum integer digits: ".08"
      * <li>One minimum integer digit: "0.08"
      * <li>Two minimum integer digits: "00.08"
      * </ul>
      *
      * <p>
      * Pass this method the return value of {@link IntegerWidth#zeroFillTo}. For example:
      *
      * <pre>
      * NumberFormatter::with().integerWidth(IntegerWidth::zeroFillTo(2))
      * </pre>
      *
      * The default is to have one minimum integer digit.
      *
      * @param style
      *            The integer width to use.
      * @return The fluent chain.
      * @see IntegerWidth
      * @stable ICU 60
      */
     Derived integerWidth(const IntegerWidth &style) const &;
 
     /**
      * Overload of integerWidth() for use on an rvalue reference.
      *
      * @param style
      *            The integer width to use.
      * @return The fluent chain.
      * @see #integerWidth
      * @stable ICU 62
      */
     Derived integerWidth(const IntegerWidth &style) &&;
 
     /**
      * Specifies the symbols (decimal separator, grouping separator, percent sign, numerals, etc.) to use when rendering
      * numbers.
      *
      * <ul>
      * <li><em>en_US</em> symbols: "12,345.67"
      * <li><em>fr_FR</em> symbols: "12&nbsp;345,67"
      * <li><em>de_CH</em> symbols: "12’345.67"
      * <li><em>my_MY</em> symbols: "၁၂,၃၄၅.၆၇"
      * </ul>
      *
      * <p>
      * Pass this method an instance of {@link DecimalFormatSymbols}. For example:
      *
      * <pre>
      * NumberFormatter::with().symbols(DecimalFormatSymbols(Locale("de_CH"), status))
      * </pre>
      *
      * <p>
      * <strong>Note:</strong> DecimalFormatSymbols automatically chooses the best numbering system based on the locale.
      * In the examples above, the first three are using the Latin numbering system, and the fourth is using the Myanmar
      * numbering system.
      *
      * <p>
      * <strong>Note:</strong> The instance of DecimalFormatSymbols will be copied: changes made to the symbols object
      * after passing it into the fluent chain will not be seen.
      *
      * <p>
      * <strong>Note:</strong> Calling this method will override any previously specified DecimalFormatSymbols
      * or NumberingSystem.
      *
      * <p>
      * The default is to choose the symbols based on the locale specified in the fluent chain.
      *
      * @param symbols
      *            The DecimalFormatSymbols to use.
      * @return The fluent chain.
      * @see DecimalFormatSymbols
      * @stable ICU 60
      */
     Derived symbols(const DecimalFormatSymbols &symbols) const &;
 
     /**
      * Overload of symbols() for use on an rvalue reference.
      *
      * @param symbols
      *            The DecimalFormatSymbols to use.
      * @return The fluent chain.
      * @see #symbols
      * @stable ICU 62
      */
     Derived symbols(const DecimalFormatSymbols &symbols) &&;
 
     /**
      * Specifies that the given numbering system should be used when fetching symbols.
      *
      * <ul>
      * <li>Latin numbering system: "12,345"
      * <li>Myanmar numbering system: "၁၂,၃၄၅"
      * <li>Math Sans Bold numbering system: "𝟭𝟮,𝟯𝟰𝟱"
      * </ul>
      *
      * <p>
      * Pass this method an instance of {@link NumberingSystem}. For example, to force the locale to always use the Latin
      * alphabet numbering system (ASCII digits):
      *
      * <pre>
      * NumberFormatter::with().adoptSymbols(NumberingSystem::createInstanceByName("latn", status))
      * </pre>
      *
      * <p>
      * <strong>Note:</strong> Calling this method will override any previously specified DecimalFormatSymbols
      * or NumberingSystem.
      *
      * <p>
      * The default is to choose the best numbering system for the locale.
      *
      * <p>
      * This method takes ownership of a pointer in order to work nicely with the NumberingSystem factory methods.
      *
      * @param symbols
      *            The NumberingSystem to use.
      * @return The fluent chain.
      * @see NumberingSystem
      * @stable ICU 60
      */
     Derived adoptSymbols(NumberingSystem *symbols) const &;
 
     /**
      * Overload of adoptSymbols() for use on an rvalue reference.
      *
      * @param symbols
      *            The NumberingSystem to use.
      * @return The fluent chain.
      * @see #adoptSymbols
      * @stable ICU 62
      */
     Derived adoptSymbols(NumberingSystem *symbols) &&;
 
     /**
      * Sets the width of the unit (measure unit or currency).  Most common values:
      *
      * <ul>
      * <li>Short: "$12.00", "12 m"
      * <li>ISO Code: "USD 12.00"
      * <li>Full name: "12.00 US dollars", "12 meters"
      * </ul>
      *
      * <p>
      * Pass an element from the {@link UNumberUnitWidth} enum to this setter. For example:
      *
      * <pre>
      * NumberFormatter::with().unitWidth(UNumberUnitWidth::UNUM_UNIT_WIDTH_FULL_NAME)
      * </pre>
      *
      * <p>
      * The default is the SHORT width.
      *
      * @param width
      *            The width to use when rendering numbers.
      * @return The fluent chain
      * @see UNumberUnitWidth
      * @stable ICU 60
      */
     Derived unitWidth(UNumberUnitWidth width) const &;
 
     /**
      * Overload of unitWidth() for use on an rvalue reference.
      *
      * @param width
      *            The width to use when rendering numbers.
      * @return The fluent chain.
      * @see #unitWidth
      * @stable ICU 62
      */
     Derived unitWidth(UNumberUnitWidth width) &&;
 
     /**
      * Sets the plus/minus sign display strategy. Most common values:
      *
      * <ul>
      * <li>Auto: "123", "-123"
      * <li>Always: "+123", "-123"
      * <li>Accounting: "$123", "($123)"
      * </ul>
      *
      * <p>
      * Pass an element from the {@link UNumberSignDisplay} enum to this setter. For example:
      *
      * <pre>
      * NumberFormatter::with().sign(UNumberSignDisplay::UNUM_SIGN_ALWAYS)
      * </pre>
      *
      * <p>
      * The default is AUTO sign display.
      *
      * @param style
      *            The sign display strategy to use when rendering numbers.
      * @return The fluent chain
      * @see UNumberSignDisplay
      * @stable ICU 60
      */
     Derived sign(UNumberSignDisplay style) const &;
 
     /**
      * Overload of sign() for use on an rvalue reference.
      *
      * @param style
      *            The sign display strategy to use when rendering numbers.
      * @return The fluent chain.
      * @see #sign
      * @stable ICU 62
      */
     Derived sign(UNumberSignDisplay style) &&;
 
     /**
      * Sets the decimal separator display strategy. This affects integer numbers with no fraction part. Most common
      * values:
      *
      * <ul>
      * <li>Auto: "1"
      * <li>Always: "1."
      * </ul>
      *
      * <p>
      * Pass an element from the {@link UNumberDecimalSeparatorDisplay} enum to this setter. For example:
      *
      * <pre>
      * NumberFormatter::with().decimal(UNumberDecimalSeparatorDisplay::UNUM_DECIMAL_SEPARATOR_ALWAYS)
      * </pre>
      *
      * <p>
      * The default is AUTO decimal separator display.
      *
      * @param style
      *            The decimal separator display strategy to use when rendering numbers.
      * @return The fluent chain
      * @see UNumberDecimalSeparatorDisplay
      * @stable ICU 60
      */
     Derived decimal(UNumberDecimalSeparatorDisplay style) const &;
 
     /**
      * Overload of decimal() for use on an rvalue reference.
      *
      * @param style
      *            The decimal separator display strategy to use when rendering numbers.
      * @return The fluent chain.
      * @see #decimal
      * @stable ICU 62
      */
     Derived decimal(UNumberDecimalSeparatorDisplay style) &&;
 
     /**
      * Sets a scale (multiplier) to be used to scale the number by an arbitrary amount before formatting.
      * Most common values:
      *
      * <ul>
      * <li>Multiply by 100: useful for percentages.
      * <li>Multiply by an arbitrary value: useful for unit conversions.
      * </ul>
      *
      * <p>
      * Pass an element from a {@link Scale} factory method to this setter. For example:
      *
      * <pre>
      * NumberFormatter::with().scale(Scale::powerOfTen(2))
      * </pre>
      *
      * <p>
      * The default is to not apply any multiplier.
      *
      * @param scale
      *            The scale to apply when rendering numbers.
      * @return The fluent chain
      * @stable ICU 62
      */
     Derived scale(const Scale &scale) const &;
 
     /**
      * Overload of scale() for use on an rvalue reference.
      *
      * @param scale
      *            The scale to apply when rendering numbers.
      * @return The fluent chain.
      * @see #scale
      * @stable ICU 62
      */
     Derived scale(const Scale &scale) &&;
 
     /**
      * Specifies the usage for which numbers will be formatted ("person-height",
      * "road", "rainfall", etc.)
      *
      * When a `usage` is specified, the output unit will change depending on the
      * `Locale` and the unit quantity. For example, formatting length
      * measurements specified in meters:
      *
      * `NumberFormatter::with().usage("person").unit(MeasureUnit::getMeter()).locale("en-US")`
      *   * When formatting 0.25, the output will be "10 inches".
      *   * When formatting 1.50, the output will be "4 feet and 11 inches".
      *
      * The input unit specified via unit() determines the type of measurement
      * being formatted (e.g. "length" when the unit is "foot"). The usage
      * requested will be looked for only within this category of measurement
      * units.
      *
      * The output unit can be found via FormattedNumber::getOutputUnit().
      *
      * If the usage has multiple parts (e.g. "land-agriculture-grain") and does
      * not match a known usage preference, the last part will be dropped
      * repeatedly until a match is found (e.g. trying "land-agriculture", then
      * "land"). If a match is still not found, usage will fall back to
      * "default".
      *
      * Setting usage to an empty string clears the usage (disables usage-based
      * localized formatting).
      *
      * Setting a usage string but not a correct input unit will result in an
      * U_ILLEGAL_ARGUMENT_ERROR.
      *
      * When using usage, specifying rounding or precision is unnecessary.
      * Specifying a precision in some manner will override the default
      * formatting.
      *
      * @param usage A `usage` parameter from the units resource. See the
      * unitPreferenceData in *source/data/misc/units.txt*, generated from
      * `unitPreferenceData` in [CLDR's
      * supplemental/units.xml](https://github.com/unicode-org/cldr/blob/main/common/supplemental/units.xml).
      * @return The fluent chain.
      * @stable ICU 68
      */
     Derived usage(StringPiece usage) const &;
 
     /**
      * Overload of usage() for use on an rvalue reference.
      *
      * @param usage The unit `usage`.
      * @return The fluent chain.
      * @stable ICU 68
      */
     Derived usage(StringPiece usage) &&;
 
     /**
      * Specifies the DisplayOptions. For example, UDisplayOptionsGrammaticalCase specifies
      * the desired case for a unit formatter's output (e.g. accusative, dative, genitive).
      *
      * @param displayOptions
      * @return The fluent chain.
      * @stable ICU 72
      */
     Derived displayOptions(const DisplayOptions &displayOptions) const &;
 
     /**
      * Overload of displayOptions() for use on an rvalue reference.
      *
      * @param displayOptions
      * @return The fluent chain.
      * @stable ICU 72
      */
     Derived displayOptions(const DisplayOptions &displayOptions) &&;
 
 #ifndef U_HIDE_INTERNAL_API
     /**
      * NOTE: Use `displayOptions` instead. This method was part of
      * an internal technology preview in ICU 69, but will be removed
      * in ICU 73, in favor of `displayOptions`
      *
      * Specifies the desired case for a unit formatter's output (e.g.
      * accusative, dative, genitive).
      *
      * @internal
      */
     Derived unitDisplayCase(StringPiece unitDisplayCase) const &;
 
     /**
      * NOTE: Use `displayOptions` instead. This method was part of
      * an internal technology preview in ICU 69, but will be removed
      * in ICU 73, in favor of `displayOptions`
      *
      * Overload of unitDisplayCase() for use on an rvalue reference.
      *
      * @internal
      */
     Derived unitDisplayCase(StringPiece unitDisplayCase) &&;
 #endif // U_HIDE_INTERNAL_API
 
 #ifndef U_HIDE_INTERNAL_API
 
     /**
      * Set the padding strategy. May be added in the future; see #13338.
      *
      * @internal ICU 60: This API is ICU internal only.
      */
     Derived padding(const impl::Padder &padder) const &;
 
     /** @internal */
     Derived padding(const impl::Padder &padder) &&;
 
     /**
      * Internal fluent setter to support a custom regulation threshold. A threshold of 1 causes the data structures to
      * be built right away. A threshold of 0 prevents the data structures from being built.
      *
      * @internal ICU 60: This API is ICU internal only.
      */
     Derived threshold(int32_t threshold) const &;
 
     /** @internal */
     Derived threshold(int32_t threshold) &&;
 
     /**
      * Internal fluent setter to overwrite the entire macros object.
      *
      * @internal ICU 60: This API is ICU internal only.
      */
     Derived macros(const impl::MacroProps& macros) const &;
 
     /** @internal */
     Derived macros(const impl::MacroProps& macros) &&;
 
     /** @internal */
     Derived macros(impl::MacroProps&& macros) const &;
 
     /** @internal */
     Derived macros(impl::MacroProps&& macros) &&;
 
 #endif  /* U_HIDE_INTERNAL_API */
 
     /**
      * Creates a skeleton string representation of this number formatter. A skeleton string is a
      * locale-agnostic serialized form of a number formatter.
      *
      * Not all options are capable of being represented in the skeleton string; for example, a
      * DecimalFormatSymbols object. If any such option is encountered, the error code is set to
      * U_UNSUPPORTED_ERROR.
      *
      * The returned skeleton is in normalized form, such that two number formatters with equivalent
      * behavior should produce the same skeleton.
      *
      * For more information on number skeleton strings, see:
      * https://unicode-org.github.io/icu/userguide/format_parse/numbers/skeletons.html
      *
      * @return A number skeleton string with behavior corresponding to this number formatter.
      * @stable ICU 62
      */
     UnicodeString toSkeleton(UErrorCode& status) const;
 
     /**
      * Returns the current (Un)LocalizedNumberFormatter as a LocalPointer
      * wrapping a heap-allocated copy of the current object.
      *
      * This is equivalent to new-ing the move constructor with a value object
      * as the argument.
      *
      * @return A wrapped (Un)LocalizedNumberFormatter pointer, or a wrapped
      *         nullptr on failure.
      * @stable ICU 64
      */
     LocalPointer<Derived> clone() const &;
 
     /**
      * Overload of clone for use on an rvalue reference.
      *
      * @return A wrapped (Un)LocalizedNumberFormatter pointer, or a wrapped
      *         nullptr on failure.
      * @stable ICU 64
      */
     LocalPointer<Derived> clone() &&;
 
     /**
      * Sets the UErrorCode if an error occurred in the fluent chain.
      * Preserves older error codes in the outErrorCode.
      * @return true if U_FAILURE(outErrorCode)
      * @stable ICU 60
      */
     UBool copyErrorTo(UErrorCode &outErrorCode) const {
         if (U_FAILURE(outErrorCode)) {
             // Do not overwrite the older error code
             return true;
         }
         fMacros.copyErrorTo(outErrorCode);
         return U_FAILURE(outErrorCode);
     }
 
     // NOTE: Uses default copy and move constructors.
 
   private:
     impl::MacroProps fMacros;
 
     // Don't construct me directly!  Use (Un)LocalizedNumberFormatter.
     NumberFormatterSettings() = default;
 
     friend class LocalizedNumberFormatter;
     friend class UnlocalizedNumberFormatter;
 
     // Give NumberRangeFormatter access to the MacroProps
     friend void impl::touchRangeLocales(impl::RangeMacroProps& macros);
     friend class impl::NumberRangeFormatterImpl;
 };
 
 // Explicit instantiations in source/i18n/number_fluent.cpp.
 // (MSVC treats imports/exports of explicit instantiations differently.)
 #ifndef _MSC_VER
 extern template class NumberFormatterSettings<UnlocalizedNumberFormatter>;
 extern template class NumberFormatterSettings<LocalizedNumberFormatter>;
 #endif
 
 /**
  * A NumberFormatter that does not yet have a locale. In order to format numbers, a locale must be specified.
  *
  * Instances of this class are immutable and thread-safe.
  *
  * @see NumberFormatter
  * @stable ICU 60
  */
 class U_I18N_API UnlocalizedNumberFormatter
         : public NumberFormatterSettings<UnlocalizedNumberFormatter>, public UMemory {
 
   public:
     /**
      * Associate the given locale with the number formatter. The locale is used for picking the appropriate symbols,
      * formats, and other data for number display.
      *
      * @param locale
      *            The locale to use when loading data for number formatting.
      * @return The fluent chain.
      * @stable ICU 60
      */
     LocalizedNumberFormatter locale(const icu::Locale &locale) const &;
 
     /**
      * Overload of locale() for use on an rvalue reference.
      *
      * @param locale
      *            The locale to use when loading data for number formatting.
      * @return The fluent chain.
      * @see #locale
      * @stable ICU 62
      */
     LocalizedNumberFormatter locale(const icu::Locale &locale) &&;
 
     /**
      * Default constructor: puts the formatter into a valid but undefined state.
      *
      * @stable ICU 62
      */
     UnlocalizedNumberFormatter() = default;
 
     /**
      * Returns a copy of this UnlocalizedNumberFormatter.
      * @stable ICU 60
      */
     UnlocalizedNumberFormatter(const UnlocalizedNumberFormatter &other);
 
     /**
      * Move constructor:
      * The source UnlocalizedNumberFormatter will be left in a valid but undefined state.
      * @stable ICU 62
      */
     UnlocalizedNumberFormatter(UnlocalizedNumberFormatter&& src) noexcept;
 
     /**
      * Copy assignment operator.
      * @stable ICU 62
      */
     UnlocalizedNumberFormatter& operator=(const UnlocalizedNumberFormatter& other);
 
     /**
      * Move assignment operator:
      * The source UnlocalizedNumberFormatter will be left in a valid but undefined state.
      * @stable ICU 62
      */
     UnlocalizedNumberFormatter& operator=(UnlocalizedNumberFormatter&& src) noexcept;
 
   private:
     explicit UnlocalizedNumberFormatter(const NumberFormatterSettings<UnlocalizedNumberFormatter>& other);
 
     explicit UnlocalizedNumberFormatter(
             NumberFormatterSettings<UnlocalizedNumberFormatter>&& src) noexcept;
 
     // To give the fluent setters access to this class's constructor:
     friend class NumberFormatterSettings<UnlocalizedNumberFormatter>;
 
     // To give NumberFormatter::with() access to this class's constructor:
     friend class NumberFormatter;
 };
 
 /**
  * A NumberFormatter that has a locale associated with it; this means .format() methods are available.
  *
  * Instances of this class are immutable and thread-safe.
  *
  * @see NumberFormatter
  * @stable ICU 60
  */
 class U_I18N_API LocalizedNumberFormatter
         : public NumberFormatterSettings<LocalizedNumberFormatter>, public UMemory {
   public:
     /**
      * Format the given integer number to a string using the settings specified in the NumberFormatter fluent
      * setting chain.
      *
      * @param value
      *            The number to format.
      * @param status
      *            Set to an ErrorCode if one occurred in the setter chain or during formatting.
      * @return A FormattedNumber object; call .toString() to get the string.
      * @stable ICU 60
      */
     FormattedNumber formatInt(int64_t value, UErrorCode &status) const;
 
     /**
      * Format the given float or double to a string using the settings specified in the NumberFormatter fluent setting
      * chain.
      *
      * @param value
      *            The number to format.
      * @param status
      *            Set to an ErrorCode if one occurred in the setter chain or during formatting.
      * @return A FormattedNumber object; call .toString() to get the string.
      * @stable ICU 60
      */
     FormattedNumber formatDouble(double value, UErrorCode &status) const;
 
     /**
      * Format the given decimal number to a string using the settings
      * specified in the NumberFormatter fluent setting chain.
      * The syntax of the unformatted number is a "numeric string"
      * as defined in the Decimal Arithmetic Specification, available at
      * http://speleotrove.com/decimal
      *
      * @param value
      *            The number to format.
      * @param status
      *            Set to an ErrorCode if one occurred in the setter chain or during formatting.
      * @return A FormattedNumber object; call .toString() to get the string.
      * @stable ICU 60
      */
     FormattedNumber formatDecimal(StringPiece value, UErrorCode& status) const;
 
 #ifndef U_HIDE_INTERNAL_API
 
             
     /**
      * @internal
      */
     const DecimalFormatSymbols* getDecimalFormatSymbols() const;
     
     /** Internal method.
      * @internal
      */
     FormattedNumber formatDecimalQuantity(const impl::DecimalQuantity& dq, UErrorCode& status) const;
 
     /** Internal method for DecimalFormat compatibility.
      * @internal
      */
     void getAffixImpl(bool isPrefix, bool isNegative, UnicodeString& result, UErrorCode& status) const;
 
     /**
      * Internal method for testing.
      * @internal
      */
     const impl::NumberFormatterImpl* getCompiled() const;
 
     /**
      * Internal method for testing.
      * @internal
      */
     int32_t getCallCount() const;
 
 #endif  /* U_HIDE_INTERNAL_API */
 
     /**
      * Creates a representation of this LocalizedNumberFormat as an icu::Format, enabling the use
      * of this number formatter with APIs that need an object of that type, such as MessageFormat.
      *
      * This API is not intended to be used other than for enabling API compatibility. The formatDouble,
      * formatInt, and formatDecimal methods should normally be used when formatting numbers, not the Format
      * object returned by this method.
      *
      * The caller owns the returned object and must delete it when finished.
      *
      * @return A Format wrapping this LocalizedNumberFormatter.
      * @stable ICU 62
      */
     Format* toFormat(UErrorCode& status) const;
 
     /**
      * Default constructor: puts the formatter into a valid but undefined state.
      *
      * @stable ICU 62
      */
     LocalizedNumberFormatter() = default;
 
     /**
      * Returns a copy of this LocalizedNumberFormatter.
      * @stable ICU 60
      */
     LocalizedNumberFormatter(const LocalizedNumberFormatter &other);
 
     /**
      * Move constructor:
      * The source LocalizedNumberFormatter will be left in a valid but undefined state.
      * @stable ICU 62
      */
     LocalizedNumberFormatter(LocalizedNumberFormatter&& src) noexcept;
 
     /**
      * Copy assignment operator.
      * @stable ICU 62
      */
     LocalizedNumberFormatter& operator=(const LocalizedNumberFormatter& other);
 
     /**
      * Move assignment operator:
      * The source LocalizedNumberFormatter will be left in a valid but undefined state.
      * @stable ICU 62
      */
     LocalizedNumberFormatter& operator=(LocalizedNumberFormatter&& src) noexcept;
 
 #ifndef U_HIDE_INTERNAL_API
 
     /**
      * This is the core entrypoint to the number formatting pipeline. It performs self-regulation: a static code path
      * for the first few calls, and compiling a more efficient data structure if called repeatedly.
      *
      * <p>
      * This function is very hot, being called in every call to the number formatting pipeline.
      *
      * @param results
      *            The results object. This method will mutate it to save the results.
      * @param status
      * @internal
      */
     void formatImpl(impl::UFormattedNumberData *results, UErrorCode &status) const;
 
 #endif  /* U_HIDE_INTERNAL_API */
 
     /**
      * Destruct this LocalizedNumberFormatter, cleaning up any memory it might own.
      * @stable ICU 60
      */
     ~LocalizedNumberFormatter();
 
   private:
     // Note: fCompiled can't be a LocalPointer because impl::NumberFormatterImpl is defined in an internal
     // header, and LocalPointer needs the full class definition in order to delete the instance.
     const impl::NumberFormatterImpl* fCompiled {nullptr};
     char fUnsafeCallCount[8] {};  // internally cast to u_atomic_int32_t
 
     // Owned pointer to a DecimalFormatWarehouse, used when copying a LocalizedNumberFormatter
     // from a DecimalFormat.
     const impl::DecimalFormatWarehouse* fWarehouse {nullptr};
 
     explicit LocalizedNumberFormatter(const NumberFormatterSettings<LocalizedNumberFormatter>& other);
 
     explicit LocalizedNumberFormatter(NumberFormatterSettings<LocalizedNumberFormatter>&& src) noexcept;
 
     LocalizedNumberFormatter(const impl::MacroProps &macros, const Locale &locale);
 
     LocalizedNumberFormatter(impl::MacroProps &&macros, const Locale &locale);
 
     void resetCompiled();
 
     void lnfMoveHelper(LocalizedNumberFormatter&& src);
 
     void lnfCopyHelper(const LocalizedNumberFormatter& src, UErrorCode& status);
 
     /**
      * @return true if the compiled formatter is available.
      */
     bool computeCompiled(UErrorCode& status) const;
 
     // To give the fluent setters access to this class's constructor:
     friend class NumberFormatterSettings<UnlocalizedNumberFormatter>;
     friend class NumberFormatterSettings<LocalizedNumberFormatter>;
 
     // To give UnlocalizedNumberFormatter::locale() access to this class's constructor:
     friend class UnlocalizedNumberFormatter;
 };
 
 #if (U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN) && defined(_MSC_VER)
 // Warning 4661.
 #pragma warning(pop)
 #endif
 
 /**
  * See the main description in numberformatter.h for documentation and examples.
  *
  * @stable ICU 60
  */
 class U_I18N_API NumberFormatter final {
   public:
     /**
      * Call this method at the beginning of a NumberFormatter fluent chain in which the locale is not currently known at
      * the call site.
      *
      * @return An {@link UnlocalizedNumberFormatter}, to be used for chaining.
      * @stable ICU 60
      */
     static UnlocalizedNumberFormatter with();
 
     /**
      * Call this method at the beginning of a NumberFormatter fluent chain in which the locale is known at the call
      * site.
      *
      * @param locale
      *            The locale from which to load formats and symbols for number formatting.
      * @return A {@link LocalizedNumberFormatter}, to be used for chaining.
      * @stable ICU 60
      */
     static LocalizedNumberFormatter withLocale(const Locale &locale);
 
     /**
      * Call this method at the beginning of a NumberFormatter fluent chain to create an instance based
      * on a given number skeleton string.
      *
      * It is possible for an error to occur while parsing. See the overload of this method if you are
      * interested in the location of a possible parse error.
      *
      * For more information on number skeleton strings, see:
      * https://unicode-org.github.io/icu/userguide/format_parse/numbers/skeletons.html
      *
      * @param skeleton
      *            The skeleton string off of which to base this NumberFormatter.
      * @param status
      *            Set to U_NUMBER_SKELETON_SYNTAX_ERROR if the skeleton was invalid.
      * @return An UnlocalizedNumberFormatter, to be used for chaining.
      * @stable ICU 62
      */
     static UnlocalizedNumberFormatter forSkeleton(const UnicodeString& skeleton, UErrorCode& status);
 
     /**
      * Call this method at the beginning of a NumberFormatter fluent chain to create an instance based
      * on a given number skeleton string.
      *
      * If an error occurs while parsing the skeleton string, the offset into the skeleton string at
      * which the error occurred will be saved into the UParseError, if provided.
      *
      * For more information on number skeleton strings, see:
      * https://unicode-org.github.io/icu/userguide/format_parse/numbers/skeletons.html
      *
      * @param skeleton
      *            The skeleton string off of which to base this NumberFormatter.
      * @param perror
      *            A parse error struct populated if an error occurs when parsing.
  *                If no error occurs, perror.offset will be set to -1.
      * @param status
      *            Set to U_NUMBER_SKELETON_SYNTAX_ERROR if the skeleton was invalid.
      * @return An UnlocalizedNumberFormatter, to be used for chaining.
      * @stable ICU 64
      */
     static UnlocalizedNumberFormatter forSkeleton(const UnicodeString& skeleton,
                                                   UParseError& perror, UErrorCode& status);
 
     /**
      * Use factory methods instead of the constructor to create a NumberFormatter.
      */
     NumberFormatter() = delete;
 };
 
 }  // namespace number
 U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // __NUMBERFORMATTER_H__

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