text: // © 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/fieldpos.h"
  #include "unicode/formattedvalue.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"
  
  /**
   * \file
   * \brief C++ API: Library for localized number formatting introduced in ICU 60.
   *
   * This library was introduced in ICU 60 to simplify the process of formatting localized number strings.
   * Basic usage examples:
   *
   * <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>.
   *
   * @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 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;
  
  /**
   * 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 */
          struct ScientificSettings {
              /** @internal */
              int8_t fEngineeringInterval;
              /** @internal */
              bool fRequireMinInt;
              /** @internal */
              impl::digits_t fMinExponentDigits;
              /** @internal */
              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);
  
      /**
       * 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);
  
    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 */
          struct FractionSignificantSettings {
              // For RND_FRACTION, RND_SIGNIFICANT, and RND_FRACTION_SIGNIFICANT
              /** @internal */
              impl::digits_t fMinFrac;
              /** @internal */
              impl::digits_t fMaxFrac;
              /** @internal */
              impl::digits_t fMinSig;
              /** @internal */
              impl::digits_t fMaxSig;
          } fracSig;
          /** @internal */
          struct IncrementSettings {
              // For RND_INCREMENT, RND_INCREMENT_ONE, and RND_INCREMENT_FIVE
              /** @internal */
              double fIncrement;
              /** @internal */
              impl::digits_t fMinFrac;
              /** @internal */
              impl::digits_t fMaxFrac;
          } increment;
          UCurrencyUsage currencyUsage; // For RND_CURRENCY
          UErrorCode errorCode; // For RND_ERROR
      } fUnion;
  
      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);
  
      static IncrementPrecision constructIncrement(double increment, int32_t minFrac);
  
      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:
      /**
       * Ensure that no less than this number of significant digits are retained when rounding according to fraction
       * rules.
       *
       * <p>
       * For example, with integer rounding, the number 3.141 becomes "3". However, with minimum figures set to 2, 3.141
       * becomes "3.1" instead.
       *
       * <p>
       * This setting does not affect the number of trailing zeros. For example, 3.01 would print as "3", not "3.0".
       *
       * @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.
       *
       * <p>
       * For example, with integer rounding, the number 123.4 becomes "123". However, with maximum figures set to 2, 123.4
       * becomes "120" instead.
       *
       * <p>
       * This setting does not affect the number of trailing zeros. For example, with fixed fraction of 2, 123.4 would
       * become "120.00".
       *
       * @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) U_NOEXCEPT;
  
      /** @stable ICU 62 */
      Scale& operator=(Scale&& src) U_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 Usage with #ifndef U_HIDE_INTERNAL_API, needed for a protected field
  /**
   * Manages NumberFormatterSettings::usage()'s char* instance on the heap.
   * @internal
   */
  class U_I18N_API Usage : public UMemory {
  
  #ifndef U_HIDE_INTERNAL_API
  
    public:
      /** @internal */
      Usage(const Usage& other);
  
      /** @internal */
      Usage& operator=(const Usage& other);
  
      /** @internal */
      Usage(Usage &&src) U_NOEXCEPT;
  
      /** @internal */
      Usage& operator=(Usage&& src) U_NOEXCEPT;
  
      /** @internal */
      ~Usage();
  
      /** @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 *fUsage;
      int16_t fLength;
      UErrorCode fError;
  
      Usage() : fUsage(nullptr), fLength(0), fError(U_ZERO_ERROR) {}
  
      /** @internal */
      UBool copyErrorTo(UErrorCode &status) const {
          if (U_FAILURE(fError)) {
              status = fError;
              return true;
          }
          return false;
      }
  
      // Allow NumberFormatterImpl to access fUsage.
      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) U_NOEXCEPT;
  
      /** @internal */
      SymbolsWrapper &operator=(SymbolsWrapper&& src) U_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;
  
      // To allow NumberFormatterImpl to access isBogus() and perform other operations:
      friend class NumberFormatterImpl;
  
      // 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 */
      UNumberDecimalSeparatorDisplay decimal = UNUM_DECIMAL_SEPARATOR_COUNT;
  
      /** @internal */
      Scale scale;  // = Scale();  (benign value)
  
      /** @internal */
      Usage usage;  // = Usage();  (no usage)
  
      /** @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);
      }
  };
  
  } // 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) &&;
  
  #ifndef U_HIDE_DRAFT_API
      /**
       * 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/master/common/supplemental/units.xml).
       * @return The fluent chain.
       * @draft 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.
       * @draft ICU 68
       */
      Derived usage(StringPiece usage) &&;
  #endif // U_HIDE_DRAFT_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.
       *
       * @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;
  };
  
  /**
   * 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) U_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) U_NOEXCEPT;
  
    private:
      explicit UnlocalizedNumberFormatter(const NumberFormatterSettings<UnlocalizedNumberFormatter>& other);
  
      explicit UnlocalizedNumberFormatter(
              NumberFormatterSettings<UnlocalizedNumberFormatter>&& src) U_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 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) U_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) U_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) U_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
  
  /**
   * The result of a number formatting operation. This class allows the result to be exported in several data types,
   * including a UnicodeString and a FieldPositionIterator.
   *
   * Instances of this class are immutable and thread-safe.
   *
   * @stable ICU 60
   */
  class U_I18N_API FormattedNumber : public UMemory, public FormattedValue {
    public:
  
      /**
       * Default constructor; makes an empty FormattedNumber.
       * @stable ICU 64
       */
      FormattedNumber()
          : fData(nullptr), fErrorCode(U_INVALID_STATE_ERROR) {}
  
      /**
       * Move constructor: Leaves the source FormattedNumber in an undefined state.
       * @stable ICU 62
       */
      FormattedNumber(FormattedNumber&& src) U_NOEXCEPT;
  
      /**
       * Destruct an instance of FormattedNumber.
       * @stable ICU 60
       */
      virtual ~FormattedNumber() U_OVERRIDE;
  
      /** Copying not supported; use move constructor instead. */
      FormattedNumber(const FormattedNumber&) = delete;
  
      /** Copying not supported; use move assignment instead. */
      FormattedNumber& operator=(const FormattedNumber&) = delete;
  
      /**
       * Move assignment: Leaves the source FormattedNumber in an undefined state.
       * @stable ICU 62
       */
      FormattedNumber& operator=(FormattedNumber&& src) U_NOEXCEPT;
  
      // Copybrief: this method is older than the parent method
      /**
       * @copybrief FormattedValue::toString()
       *
       * For more information, see FormattedValue::toString()
       *
       * @stable ICU 62
       */
      UnicodeString toString(UErrorCode& status) const U_OVERRIDE;
  
      // Copydoc: this method is new in ICU 64
      /** @copydoc FormattedValue::toTempString() */
      UnicodeString toTempString(UErrorCode& status) const U_OVERRIDE;
  
      // Copybrief: this method is older than the parent method
      /**
       * @copybrief FormattedValue::appendTo()
       *
       * For more information, see FormattedValue::appendTo()
       *
       * @stable ICU 62
       */
      Appendable &appendTo(Appendable& appendable, UErrorCode& status) const U_OVERRIDE;
  
      // Copydoc: this method is new in ICU 64
      /** @copydoc FormattedValue::nextPosition() */
      UBool nextPosition(ConstrainedFieldPosition& cfpos, UErrorCode& status) const U_OVERRIDE;
  
      /**
       * Export the formatted number as a "numeric string" conforming to the
       * syntax defined in the Decimal Arithmetic Specification, available at
       * http://speleotrove.com/decimal
       *
       * This endpoint is useful for obtaining the exact number being printed
       * after scaling and rounding have been applied by the number formatter.
       *
       * Example call site:
       *
       *     auto decimalNumber = fn.toDecimalNumber<std::string>(status);
       *
       * @tparam StringClass A string class compatible with StringByteSink;
       *         for example, std::string.
       * @param status Set if an error occurs.
       * @return A StringClass containing the numeric string.
       * @stable ICU 65
       */
      template<typename StringClass>
      inline StringClass toDecimalNumber(UErrorCode& status) const;
  
  #ifndef U_HIDE_DRAFT_API
  	/**
       * Gets the resolved output unit.
       *
       * The output unit is dependent upon the localized preferences for the usage
       * specified via NumberFormatterSettings::usage(), and may be a unit with
       * UMEASURE_UNIT_MIXED unit complexity (MeasureUnit::getComplexity()), such
       * as "foot-and-inch" or "hour-and-minute-and-second".
       *
       * @return `MeasureUnit`.
       * @draft ICU 68
       */
      MeasureUnit getOutputUnit(UErrorCode& status) const;
  #endif // U_HIDE_DRAFT_API
  
  #ifndef U_HIDE_INTERNAL_API
  
      /**
       *  Gets the raw DecimalQuantity for plural rule selection.
       *  @internal
       */
      void getDecimalQuantity(impl::DecimalQuantity& output, UErrorCode& status) const;
  
      /**
       * Populates the mutable builder type FieldPositionIteratorHandler.
       * @internal
       */
      void getAllFieldPositionsImpl(FieldPositionIteratorHandler& fpih, UErrorCode& status) const;
  
  #endif  /* U_HIDE_INTERNAL_API */
  
    private:
      // Can't use LocalPointer because UFormattedNumberData is forward-declared
      const impl::UFormattedNumberData *fData;
  
      // Error code for the terminal methods
      UErrorCode fErrorCode;
  
      /**
       * Internal constructor from data type. Adopts the data pointer.
       * @internal
       */
      explicit FormattedNumber(impl::UFormattedNumberData *results)
          : fData(results), fErrorCode(U_ZERO_ERROR) {}
  
      explicit FormattedNumber(UErrorCode errorCode)
          : fData(nullptr), fErrorCode(errorCode) {}
  
      void toDecimalNumber(ByteSink& sink, UErrorCode& status) const;
  
      // To give LocalizedNumberFormatter format methods access to this class's constructor:
      friend class LocalizedNumberFormatter;
  
      // To give C API access to internals
      friend struct impl::UFormattedNumberImpl;
  };
  
  #ifndef U_HIDE_DRAFT_API
  // Note: This is draft ICU 65
  template<typename StringClass>
  StringClass FormattedNumber::toDecimalNumber(UErrorCode& status) const {
      StringClass result;
      StringByteSink<StringClass> sink(&result);
      toDecimalNumber(sink, status);
      return result;
  }
  #endif // U_HIDE_DRAFT_API
  
  /**
   * 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.
       *
       * @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.
       *
       * @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__
  