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// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
********************************************************************************
* Copyright (C) 1997-2016, International Business Machines Corporation and others.
* All Rights Reserved.
********************************************************************************
*
* File NUMFMT.H
*
* Modification History:
*
*   Date        Name        Description
*   02/19/97    aliu        Converted from java.
*   03/18/97    clhuang     Updated per C++ implementation.
*   04/17/97    aliu        Changed DigitCount to int per code review.
*    07/20/98    stephen        JDK 1.2 sync up. Added scientific support.
*                            Changed naming conventions to match C++ guidelines
*                            Deprecated Java style constants (eg, INTEGER_FIELD)
********************************************************************************
*/

#ifndef NUMFMT_H
#define NUMFMT_H


#include "unicode/utypes.h"

#if U_SHOW_CPLUSPLUS_API

/**
 * \file
 * \brief C++ API: Compatibility APIs for number formatting.
 */

#if !UCONFIG_NO_FORMATTING

#include "unicode/unistr.h"
#include "unicode/format.h"
#include "unicode/unum.h" // UNumberFormatStyle
#include "unicode/locid.h"
#include "unicode/stringpiece.h"
#include "unicode/curramt.h"
#include "unicode/udisplaycontext.h"

class NumberFormatTest;

U_NAMESPACE_BEGIN

class SharedNumberFormat;

#if !UCONFIG_NO_SERVICE
class NumberFormatFactory;
class StringEnumeration;
#endif

/**
 * <p><strong>IMPORTANT:</strong> New users are strongly encouraged to see if
 * numberformatter.h fits their use case.  Although not deprecated, this header
 * is provided for backwards compatibility only.
 *
 * Abstract base class for all number formats.  Provides interface for
 * formatting and parsing a number.  Also provides methods for
 * determining which locales have number formats, and what their names
 * are.
 *
 * \headerfile unicode/numfmt.h "unicode/numfmt.h"
 * <P>
 * NumberFormat helps you to format and parse numbers for any locale.
 * Your code can be completely independent of the locale conventions
 * for decimal points, thousands-separators, or even the particular
 * decimal digits used, or whether the number format is even decimal.
 * <P>
 * To format a number for the current Locale, use one of the static
 * factory methods:
 * \code
 *    #include <iostream>
 *    #include "unicode/numfmt.h"
 *    #include "unicode/unistr.h"
 *    #include "unicode/ustream.h"
 *    using namespace std;
 *    
 *    int main() {
 *        double myNumber = 7.0;
 *        UnicodeString myString;
 *        UErrorCode success = U_ZERO_ERROR;
 *        NumberFormat* nf = NumberFormat::createInstance(success);
 *        nf->format(myNumber, myString);
 *        cout << " Example 1: " << myString << endl;
 *    }
 * \endcode
 * Note that there are additional factory methods within subclasses of
 * NumberFormat.
 * <P>
 * If you are formatting multiple numbers, it is more efficient to get
 * the format and use it multiple times so that the system doesn't
 * have to fetch the information about the local language and country
 * conventions multiple times.
 * \code
 *     UnicodeString myString;
 *     UErrorCode success = U_ZERO_ERROR;
 *     NumberFormat *nf = NumberFormat::createInstance( success );
 *     for (int32_t number: {123, 3333, -1234567}) {
 *         nf->format(number, myString);
 *         myString += "; ";
 *     }
 *     cout << " Example 2: " << myString << endl;
 * \endcode
 * To format a number for a different Locale, specify it in the
 * call to \c createInstance().
 * \code
 *     nf = NumberFormat::createInstance(Locale::getFrench(), success);
 * \endcode
 * You can use a \c NumberFormat to parse also.
 * \code
 *    UErrorCode success;
 *    Formattable result(-999);  // initialized with error code
 *    nf->parse(myString, result, success);
 * \endcode
 * Use \c createInstance() to get the normal number format for a \c Locale.
 * There are other static factory methods available.  Use \c createCurrencyInstance()
 * to get the currency number format for that country.  Use \c createPercentInstance()
 * to get a format for displaying percentages. With this format, a
 * fraction from 0.53 is displayed as 53%.
 * <P>
 * The type of number formatting can be specified by passing a 'style' parameter to \c createInstance().
 * For example, use\n
 * \c createInstance(locale, UNUM_DECIMAL, errorCode) to get the normal number format,\n
 * \c createInstance(locale, UNUM_PERCENT, errorCode) to get a format for displaying percentage,\n
 * \c createInstance(locale, UNUM_SCIENTIFIC, errorCode) to get a format for displaying scientific number,\n
 * \c createInstance(locale, UNUM_CURRENCY, errorCode) to get the currency number format,
 * in which the currency is represented by its symbol, for example, "$3.00".\n
 * \c createInstance(locale, UNUM_CURRENCY_ISO, errorCode)  to get the currency number format,
 * in which the currency is represented by its ISO code, for example "USD3.00".\n
 * \c createInstance(locale, UNUM_CURRENCY_PLURAL, errorCode) to get the currency number format,
 * in which the currency is represented by its full name in plural format,
 * for example, "3.00 US dollars" or "1.00 US dollar".
 * <P>
 * You can also control the display of numbers with such methods as
 * \c getMinimumFractionDigits().  If you want even more control over the
 * format or parsing, or want to give your users more control, you can
 * try dynamic_casting the \c NumberFormat you get from the factory methods to a
 * \c DecimalFormat. This will work for the vast majority of
 * countries; just remember to test for nullptr in case you
 * encounter an unusual one.
 * <P>
 * You can also use forms of the parse and format methods with
 * \c ParsePosition and \c FieldPosition to allow you to:
 * <ul type=round>
 *   <li>(a) progressively parse through pieces of a string.
 *   <li>(b) align the decimal point and other areas.
 * </ul>
 * For example, you can align numbers in two ways.
 * <P>
 * If you are using a monospaced font with spacing for alignment, you
 * can pass the \c FieldPosition in your format call, with field =
 * \c UNUM_INTEGER_FIELD. On output, \c getEndIndex will be set to the offset
 * between the last character of the integer and the decimal. Add
 * (desiredSpaceCount - getEndIndex) spaces at the front of the
 * string.
 * <P>
 * If you are using proportional fonts, instead of padding with
 * spaces, measure the width of the string in pixels from the start to
 * getEndIndex.  Then move the pen by (desiredPixelWidth -
 * widthToAlignmentPoint) before drawing the text.  It also works
 * where there is no decimal, but possibly additional characters at
 * the end, e.g. with parentheses in negative numbers: "(12)" for -12.
 * <p>
 * <em>User subclasses are not supported.</em> While clients may write
 * subclasses, such code will not necessarily work and will not be
 * guaranteed to work stably from release to release.
 *
 * @stable ICU 2.0
 */
class U_I18N_API NumberFormat : public Format {
public:
    /**
     * Rounding mode.
     *
     * <p>
     * For more detail on rounding modes, see:
     * https://unicode-org.github.io/icu/userguide/format_parse/numbers/rounding-modes
     *
     * @stable ICU 2.4
     */
    enum ERoundingMode {
        kRoundCeiling,  /**< Round towards positive infinity */
        kRoundFloor,    /**< Round towards negative infinity */
        kRoundDown,     /**< Round towards zero */
        kRoundUp,       /**< Round away from zero */
        kRoundHalfEven, /**< Round towards the nearest integer, or
                             towards the nearest even integer if equidistant */
        kRoundHalfDown, /**< Round towards the nearest integer, or
                             towards zero if equidistant */
        kRoundHalfUp,   /**< Round towards the nearest integer, or
                             away from zero if equidistant */
        /**
          *  Return U_FORMAT_INEXACT_ERROR if number does not format exactly.
          *  @stable ICU 4.8
          */
        kRoundUnnecessary,
        /**
         * Rounds ties toward the odd number.
         * @stable ICU 73
         */
        kRoundHalfOdd,
        /**
         * Rounds ties toward +∞.
         * @stable ICU 73
         */
        kRoundHalfCeiling,
        /**
         * Rounds ties toward -∞.
         * @stable ICU 73
         */
        kRoundHalfFloor,
    };

    /**
     * Alignment Field constants used to construct a FieldPosition object.
     * Signifies that the position of the integer part or fraction part of
     * a formatted number should be returned.
     *
     * Note: as of ICU 4.4, the values in this enum have been extended to
     * support identification of all number format fields, not just those
     * pertaining to alignment.
     *
     * These constants are provided for backwards compatibility only.
     * Please use the C style constants defined in the header file unum.h.
     *
     * @see FieldPosition
     * @stable ICU 2.0
     */
    enum EAlignmentFields {
        /** @stable ICU 2.0 */
        kIntegerField = UNUM_INTEGER_FIELD,
        /** @stable ICU 2.0 */
        kFractionField = UNUM_FRACTION_FIELD,
        /** @stable ICU 2.0 */
        kDecimalSeparatorField = UNUM_DECIMAL_SEPARATOR_FIELD,
        /** @stable ICU 2.0 */
        kExponentSymbolField = UNUM_EXPONENT_SYMBOL_FIELD,
        /** @stable ICU 2.0 */
        kExponentSignField = UNUM_EXPONENT_SIGN_FIELD,
        /** @stable ICU 2.0 */
        kExponentField = UNUM_EXPONENT_FIELD,
        /** @stable ICU 2.0 */
        kGroupingSeparatorField = UNUM_GROUPING_SEPARATOR_FIELD,
        /** @stable ICU 2.0 */
        kCurrencyField = UNUM_CURRENCY_FIELD,
        /** @stable ICU 2.0 */
        kPercentField = UNUM_PERCENT_FIELD,
        /** @stable ICU 2.0 */
        kPermillField = UNUM_PERMILL_FIELD,
        /** @stable ICU 2.0 */
        kSignField = UNUM_SIGN_FIELD,
        /** @stable ICU 64 */
        kMeasureUnitField = UNUM_MEASURE_UNIT_FIELD,
        /** @stable ICU 64 */
        kCompactField = UNUM_COMPACT_FIELD,

    /**
     * These constants are provided for backwards compatibility only.
     * Please use the constants defined in the header file unum.h.
     */
        /** @stable ICU 2.0 */
        INTEGER_FIELD        = UNUM_INTEGER_FIELD,
        /** @stable ICU 2.0 */
        FRACTION_FIELD       = UNUM_FRACTION_FIELD
    };

    /**
     * Destructor.
     * @stable ICU 2.0
     */
    virtual ~NumberFormat();

    /**
     * Clones this object polymorphically.
     * The caller owns the result and should delete it when done.
     * @return clone, or nullptr if an error occurred
     * @stable ICU 2.0
     */
    virtual NumberFormat* clone() const override = 0;

    /**
     * Return true if the given Format objects are semantically equal.
     * Objects of different subclasses are considered unequal.
     * @return    true if the given Format objects are semantically equal.
     * @stable ICU 2.0
     */
    virtual bool operator==(const Format& other) const override;


    using Format::format;

    /**
     * Format an object to produce a string.  This method handles
     * Formattable objects with numeric types. If the Formattable
     * object type is not a numeric type, then it returns a failing
     * UErrorCode.
     *
     * @param obj       The object to format.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    virtual UnicodeString& format(const Formattable& obj,
                                  UnicodeString& appendTo,
                                  FieldPosition& pos,
                                  UErrorCode& status) const override;

    /**
     * Format an object to produce a string.  This method handles
     * Formattable objects with numeric types. If the Formattable
     * object type is not a numeric type, then it returns a failing
     * UErrorCode.
     *
     * @param obj       The object to format.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.  Can be
     *                  nullptr.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 4.4
     */
    virtual UnicodeString& format(const Formattable& obj,
                                  UnicodeString& appendTo,
                                  FieldPositionIterator* posIter,
                                  UErrorCode& status) const override;

    /**
     * Parse a string to produce an object.  This methods handles
     * parsing of numeric strings into Formattable objects with numeric
     * types.
     * <P>
     * Before calling, set parse_pos.index to the offset you want to
     * start parsing at in the source. After calling, parse_pos.index
     * indicates the position after the successfully parsed text.  If
     * an error occurs, parse_pos.index is unchanged.
     * <P>
     * When parsing, leading whitespace is discarded (with successful
     * parse), while trailing whitespace is left as is.
     * <P>
     * See Format::parseObject() for more.
     *
     * @param source    The string to be parsed into an object.
     * @param result    Formattable to be set to the parse result.
     *                  If parse fails, return contents are undefined.
     * @param parse_pos The position to start parsing at. Upon return
     *                  this param is set to the position after the
     *                  last character successfully parsed. If the
     *                  source is not parsed successfully, this param
     *                  will remain unchanged.
     * @return          A newly created Formattable* object, or nullptr
     *                  on failure.  The caller owns this and should
     *                  delete it when done.
     * @stable ICU 2.0
     */
    virtual void parseObject(const UnicodeString& source,
                             Formattable& result,
                             ParsePosition& parse_pos) const override;

    /**
     * Format a double number. These methods call the NumberFormat
     * pure virtual format() methods with the default FieldPosition.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    UnicodeString& format(  double number,
                            UnicodeString& appendTo) const;

    /**
     * Format a long number. These methods call the NumberFormat
     * pure virtual format() methods with the default FieldPosition.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    UnicodeString& format(  int32_t number,
                            UnicodeString& appendTo) const;

    /**
     * Format an int64 number. These methods call the NumberFormat
     * pure virtual format() methods with the default FieldPosition.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.8
     */
    UnicodeString& format(  int64_t number,
                            UnicodeString& appendTo) const;

    /**
     * Format a double number. Concrete subclasses must implement
     * these pure virtual methods.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    virtual UnicodeString& format(double number,
                                  UnicodeString& appendTo,
                                  FieldPosition& pos) const = 0;
    /**
     * Format a double number. By default, the parent function simply
     * calls the base class and does not return an error status.
     * Therefore, the status may be ignored in some subclasses.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @param status    error status
     * @return          Reference to 'appendTo' parameter.
     * @internal
     */
    virtual UnicodeString& format(double number,
                                  UnicodeString& appendTo,
                                  FieldPosition& pos,
                                  UErrorCode &status) const;
    /**
     * Format a double number. Subclasses must implement
     * this method.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.
     *                  Can be nullptr.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 4.4
     */
    virtual UnicodeString& format(double number,
                                  UnicodeString& appendTo,
                                  FieldPositionIterator* posIter,
                                  UErrorCode& status) const;
    /**
     * Format a long number. Concrete subclasses must implement
     * these pure virtual methods.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
    */
    virtual UnicodeString& format(int32_t number,
                                  UnicodeString& appendTo,
                                  FieldPosition& pos) const = 0;

    /**
     * Format a long number. Concrete subclasses may override
     * this function to provide status return.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @param status the output status.
     * @return          Reference to 'appendTo' parameter.
     * @internal
    */
    virtual UnicodeString& format(int32_t number,
                                  UnicodeString& appendTo,
                                  FieldPosition& pos,
                                  UErrorCode &status) const;

    /**
     * Format an int32 number. Subclasses must implement
     * this method.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.
     *                  Can be nullptr.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 4.4
     */
    virtual UnicodeString& format(int32_t number,
                                  UnicodeString& appendTo,
                                  FieldPositionIterator* posIter,
                                  UErrorCode& status) const;
    /**
     * Format an int64 number. (Not abstract to retain compatibility
     * with earlier releases, however subclasses should override this
     * method as it just delegates to format(int32_t number...);
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.8
    */
    virtual UnicodeString& format(int64_t number,
                                  UnicodeString& appendTo,
                                  FieldPosition& pos) const;

    /**
     * Format an int64 number. (Not abstract to retain compatibility
     * with earlier releases, however subclasses should override this
     * method as it just delegates to format(int32_t number...);
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @internal
    */
    virtual UnicodeString& format(int64_t number,
                                  UnicodeString& appendTo,
                                  FieldPosition& pos,
                                  UErrorCode& status) const;
    /**
     * Format an int64 number. Subclasses must implement
     * this method.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.
     *                  Can be nullptr.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 4.4
     */
    virtual UnicodeString& format(int64_t number,
                                  UnicodeString& appendTo,
                                  FieldPositionIterator* posIter,
                                  UErrorCode& status) const;

    /**
     * Format a decimal number. Subclasses must implement
     * this method.  The syntax of the unformatted number is a "numeric string"
     * as defined in the Decimal Arithmetic Specification, available at
     * http://speleotrove.com/decimal
     *
     * @param number    The unformatted number, as a string, to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.
     *                  Can be nullptr.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 4.4
     */
    virtual UnicodeString& format(StringPiece number,
                                  UnicodeString& appendTo,
                                  FieldPositionIterator* posIter,
                                  UErrorCode& status) const;

// Can't use #ifndef U_HIDE_INTERNAL_API because these are virtual methods

    /**
     * Format a decimal number.
     * The number is a DecimalQuantity wrapper onto a floating point decimal number.
     * The default implementation in NumberFormat converts the decimal number
     * to a double and formats that.  Subclasses of NumberFormat that want
     * to specifically handle big decimal numbers must override this method.
     * class DecimalFormat does so.
     *
     * @param number    The number, a DecimalQuantity format Decimal Floating Point.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @internal
     */
    virtual UnicodeString& format(const number::impl::DecimalQuantity &number,
                                  UnicodeString& appendTo,
                                  FieldPositionIterator* posIter,
                                  UErrorCode& status) const;

    /**
     * Format a decimal number.
     * The number is a DecimalQuantity wrapper onto a floating point decimal number.
     * The default implementation in NumberFormat converts the decimal number
     * to a double and formats that.  Subclasses of NumberFormat that want
     * to specifically handle big decimal numbers must override this method.
     * class DecimalFormat does so.
     *
     * @param number    The number, a DecimalQuantity format Decimal Floating Point.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @internal
     */
    virtual UnicodeString& format(const number::impl::DecimalQuantity &number,
                                  UnicodeString& appendTo,
                                  FieldPosition& pos,
                                  UErrorCode& status) const;

   /**
    * Return a long if possible (e.g. within range LONG_MAX,
    * LONG_MAX], and with no decimals), otherwise a double.  If
    * IntegerOnly is set, will stop at a decimal point (or equivalent;
    * e.g. for rational numbers "1 2/3", will stop after the 1).
    * <P>
    * If no object can be parsed, index is unchanged, and nullptr is
    * returned.
    * <P>
    * This is a pure virtual which concrete subclasses must implement.
    *
    * @param text           The text to be parsed.
    * @param result         Formattable to be set to the parse result.
    *                       If parse fails, return contents are undefined.
    * @param parsePosition  The position to start parsing at on input.
    *                       On output, moved to after the last successfully
    *                       parse character. On parse failure, does not change.
    * @stable ICU 2.0
    */
    virtual void parse(const UnicodeString& text,
                       Formattable& result,
                       ParsePosition& parsePosition) const = 0;

    /**
     * Parse a string as a numeric value, and return a Formattable
     * numeric object. This method parses integers only if IntegerOnly
     * is set.
     *
     * @param text          The text to be parsed.
     * @param result        Formattable to be set to the parse result.
     *                      If parse fails, return contents are undefined.
     * @param status        Output parameter set to a failure error code
     *                      when a failure occurs. The error code when the
     *                      string fails to parse is U_INVALID_FORMAT_ERROR,
     *                      unless overridden by a subclass.
     * @see                 NumberFormat::isParseIntegerOnly
     * @stable ICU 2.0
     */
    virtual void parse(const UnicodeString& text,
                       Formattable& result,
                       UErrorCode& status) const;

    /**
     * Parses text from the given string as a currency amount.  Unlike
     * the parse() method, this method will attempt to parse a generic
     * currency name, searching for a match of this object's locale's
     * currency display names, or for a 3-letter ISO currency code.
     * This method will fail if this format is not a currency format,
     * that is, if it does not contain the currency pattern symbol
     * (U+00A4) in its prefix or suffix.
     *
     * @param text the string to parse
     * @param pos  input-output position; on input, the position within text
     *             to match; must have 0 <= pos.getIndex() < text.length();
     *             on output, the position after the last matched character.
     *             If the parse fails, the position in unchanged upon output.
     * @return     if parse succeeds, a pointer to a newly-created CurrencyAmount
     *             object (owned by the caller) containing information about
     *             the parsed currency; if parse fails, this is nullptr.
     * @stable ICU 49
     */
    virtual CurrencyAmount* parseCurrency(const UnicodeString& text,
                                          ParsePosition& pos) const;

    /**
     * Return true if this format will parse numbers as integers
     * only.  For example in the English locale, with ParseIntegerOnly
     * true, the string "1234." would be parsed as the integer value
     * 1234 and parsing would stop at the "." character.  Of course,
     * the exact format accepted by the parse operation is locale
     * dependent and determined by sub-classes of NumberFormat.
     * @return    true if this format will parse numbers as integers
     *            only.
     * @stable ICU 2.0
     */
    UBool isParseIntegerOnly() const;

    /**
     * Sets whether or not numbers should be parsed as integers only.
     * @param value    set True, this format will parse numbers as integers
     *                 only.
     * @see isParseIntegerOnly
     * @stable ICU 2.0
     */
    virtual void setParseIntegerOnly(UBool value);

    /**
     * Sets whether lenient parsing should be enabled (it is off by default).
     *
     * @param enable \c true if lenient parsing should be used,
     *               \c false otherwise.
     * @stable ICU 4.8
     */
    virtual void setLenient(UBool enable);

    /**
     * Returns whether lenient parsing is enabled (it is off by default).
     *
     * @return \c true if lenient parsing is enabled,
     *         \c false otherwise.
     * @see #setLenient
     * @stable ICU 4.8
     */
    virtual UBool isLenient() const;

    /**
     * Create a default style NumberFormat for the current default locale.
     * The default formatting style is locale dependent.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * {@link icu::number::NumberFormatter} instead of NumberFormat.
     * @stable ICU 2.0
     */
    static NumberFormat* U_EXPORT2 createInstance(UErrorCode&);

    /**
     * Create a default style NumberFormat for the specified locale.
     * The default formatting style is locale dependent.
     * @param inLocale    the given locale.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * {@link icu::number::NumberFormatter} instead of NumberFormat.
     * @stable ICU 2.0
     */
    static NumberFormat* U_EXPORT2 createInstance(const Locale& inLocale,
                                        UErrorCode&);

    /**
     * Create a specific style NumberFormat for the specified locale.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * {@link icu::number::NumberFormatter} instead of NumberFormat.
     * @param desiredLocale    the given locale.
     * @param style            the given style.
     * @param errorCode        Output param filled with success/failure status.
     * @return                 A new NumberFormat instance.
     * @stable ICU 4.8
     */
    static NumberFormat* U_EXPORT2 createInstance(const Locale& desiredLocale,
                                                  UNumberFormatStyle style,
                                                  UErrorCode& errorCode);

#ifndef U_HIDE_INTERNAL_API

    /**
     * ICU use only.
     * Creates NumberFormat instance without using the cache.
     * @internal
     */
    static NumberFormat* internalCreateInstance(
            const Locale& desiredLocale,
            UNumberFormatStyle style,
            UErrorCode& errorCode);

    /**
     * ICU use only.
     * Returns handle to the shared, cached NumberFormat instance for given
     * locale. On success, caller must call removeRef() on returned value
     * once it is done with the shared instance.
     * @internal
     */
    static const SharedNumberFormat* U_EXPORT2 createSharedInstance(
            const Locale& inLocale, UNumberFormatStyle style, UErrorCode& status);

#endif  /* U_HIDE_INTERNAL_API */

    /**
     * Returns a currency format for the current default locale.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * {@link icu::number::NumberFormatter} instead of NumberFormat.
     * @stable ICU 2.0
     */
    static NumberFormat* U_EXPORT2 createCurrencyInstance(UErrorCode&);

    /**
     * Returns a currency format for the specified locale.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * {@link icu::number::NumberFormatter} instead of NumberFormat.
     * @param inLocale    the given locale.
     * @stable ICU 2.0
     */
    static NumberFormat* U_EXPORT2 createCurrencyInstance(const Locale& inLocale,
                                                UErrorCode&);

    /**
     * Returns a percentage format for the current default locale.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * {@link icu::number::NumberFormatter} instead of NumberFormat.
     * @stable ICU 2.0
     */
    static NumberFormat* U_EXPORT2 createPercentInstance(UErrorCode&);

    /**
     * Returns a percentage format for the specified locale.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * {@link icu::number::NumberFormatter} instead of NumberFormat.
     * @param inLocale    the given locale.
     * @stable ICU 2.0
     */
    static NumberFormat* U_EXPORT2 createPercentInstance(const Locale& inLocale,
                                               UErrorCode&);

    /**
     * Returns a scientific format for the current default locale.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * {@link icu::number::NumberFormatter} instead of NumberFormat.
     * @stable ICU 2.0
     */
    static NumberFormat* U_EXPORT2 createScientificInstance(UErrorCode&);

    /**
     * Returns a scientific format for the specified locale.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * {@link icu::number::NumberFormatter} instead of NumberFormat.
     * @param inLocale    the given locale.
     * @stable ICU 2.0
     */
    static NumberFormat* U_EXPORT2 createScientificInstance(const Locale& inLocale,
                                                UErrorCode&);

    /**
     * Get the set of Locales for which NumberFormats are installed.
     * @param count    Output param to receive the size of the locales
     * @stable ICU 2.0
     */
    static const Locale* U_EXPORT2 getAvailableLocales(int32_t& count);

#if !UCONFIG_NO_SERVICE
    /**
     * Register a new NumberFormatFactory.  The factory will be adopted.
     * Because ICU may choose to cache NumberFormat objects internally,
     * this must be called at application startup, prior to any calls to
     * NumberFormat::createInstance to avoid undefined behavior.
     * @param toAdopt the NumberFormatFactory instance to be adopted
     * @param status the in/out status code, no special meanings are assigned
     * @return a registry key that can be used to unregister this factory
     * @stable ICU 2.6
     */
    static URegistryKey U_EXPORT2 registerFactory(NumberFormatFactory* toAdopt, UErrorCode& status);

    /**
     * Unregister a previously-registered NumberFormatFactory using the key returned from the
     * register call.  Key becomes invalid after a successful call and should not be used again.
     * The NumberFormatFactory corresponding to the key will be deleted.
     * Because ICU may choose to cache NumberFormat objects internally,
     * this should be called during application shutdown, after all calls to
     * NumberFormat::createInstance to avoid undefined behavior.
     * @param key the registry key returned by a previous call to registerFactory
     * @param status the in/out status code, no special meanings are assigned
     * @return true if the factory for the key was successfully unregistered
     * @stable ICU 2.6
     */
    static UBool U_EXPORT2 unregister(URegistryKey key, UErrorCode& status);

    /**
     * Return a StringEnumeration over the locales available at the time of the call,
     * including registered locales.
     * @return a StringEnumeration over the locales available at the time of the call
     * @stable ICU 2.6
     */
    static StringEnumeration* U_EXPORT2 getAvailableLocales();
#endif /* UCONFIG_NO_SERVICE */

    /**
     * Returns true if grouping is used in this format. For example,
     * in the English locale, with grouping on, the number 1234567
     * might be formatted as "1,234,567". The grouping separator as
     * well as the size of each group is locale dependent and is
     * determined by sub-classes of NumberFormat.
     * @see setGroupingUsed
     * @stable ICU 2.0
     */
    UBool isGroupingUsed() const;

    /**
     * Set whether or not grouping will be used in this format.
     * @param newValue    True, grouping will be used in this format.
     * @see getGroupingUsed
     * @stable ICU 2.0
     */
    virtual void setGroupingUsed(UBool newValue);

    /**
     * Returns the maximum number of digits allowed in the integer portion of a
     * number.
     * @return     the maximum number of digits allowed in the integer portion of a
     *             number.
     * @see setMaximumIntegerDigits
     * @stable ICU 2.0
     */
    int32_t getMaximumIntegerDigits() const;

    /**
     * Sets the maximum number of digits allowed in the integer portion of a
     * number. maximumIntegerDigits must be >= minimumIntegerDigits.  If the
     * new value for maximumIntegerDigits is less than the current value
     * of minimumIntegerDigits, then minimumIntegerDigits will also be set to
     * the new value.
     *
     * @param newValue    the new value for the maximum number of digits
     *                    allowed in the integer portion of a number.
     * @see getMaximumIntegerDigits
     * @stable ICU 2.0
     */
    virtual void setMaximumIntegerDigits(int32_t newValue);

    /**
     * Returns the minimum number of digits allowed in the integer portion of a
     * number.
     * @return    the minimum number of digits allowed in the integer portion of a
     *            number.
     * @see setMinimumIntegerDigits
     * @stable ICU 2.0
     */
    int32_t getMinimumIntegerDigits() const;

    /**
     * Sets the minimum number of digits allowed in the integer portion of a
     * number. minimumIntegerDigits must be &lt;= maximumIntegerDigits.  If the
     * new value for minimumIntegerDigits exceeds the current value
     * of maximumIntegerDigits, then maximumIntegerDigits will also be set to
     * the new value.
     * @param newValue    the new value to be set.
     * @see getMinimumIntegerDigits
     * @stable ICU 2.0
     */
    virtual void setMinimumIntegerDigits(int32_t newValue);

    /**
     * Returns the maximum number of digits allowed in the fraction portion of a
     * number.
     * @return    the maximum number of digits allowed in the fraction portion of a
     *            number.
     * @see setMaximumFractionDigits
     * @stable ICU 2.0
     */
    int32_t getMaximumFractionDigits() const;

    /**
     * Sets the maximum number of digits allowed in the fraction portion of a
     * number. maximumFractionDigits must be >= minimumFractionDigits.  If the
     * new value for maximumFractionDigits is less than the current value
     * of minimumFractionDigits, then minimumFractionDigits will also be set to
     * the new value.
     * @param newValue    the new value to be set.
     * @see getMaximumFractionDigits
     * @stable ICU 2.0
     */
    virtual void setMaximumFractionDigits(int32_t newValue);

    /**
     * Returns the minimum number of digits allowed in the fraction portion of a
     * number.
     * @return    the minimum number of digits allowed in the fraction portion of a
     *            number.
     * @see setMinimumFractionDigits
     * @stable ICU 2.0
     */
    int32_t getMinimumFractionDigits() const;

    /**
     * Sets the minimum number of digits allowed in the fraction portion of a
     * number. minimumFractionDigits must be &lt;= maximumFractionDigits.   If the
     * new value for minimumFractionDigits exceeds the current value
     * of maximumFractionDigits, then maximumIntegerDigits will also be set to
     * the new value
     * @param newValue    the new value to be set.
     * @see getMinimumFractionDigits
     * @stable ICU 2.0
     */
    virtual void setMinimumFractionDigits(int32_t newValue);

    /**
     * Sets the currency used to display currency
     * amounts.  This takes effect immediately, if this format is a
     * currency format.  If this format is not a currency format, then
     * the currency is used if and when this object becomes a
     * currency format.
     * @param theCurrency a 3-letter ISO code indicating new currency
     * to use.  It need not be null-terminated.  May be the empty
     * string or nullptr to indicate no currency.
     * @param ec input-output error code
     * @stable ICU 3.0
     */
    virtual void setCurrency(const char16_t* theCurrency, UErrorCode& ec);

    /**
     * Gets the currency used to display currency
     * amounts.  This may be an empty string for some subclasses.
     * @return a 3-letter null-terminated ISO code indicating
     * the currency in use, or a pointer to the empty string.
     * @stable ICU 2.6
     */
    const char16_t* getCurrency() const;

    /**
     * Set a particular UDisplayContext value in the formatter, such as
     * UDISPCTX_CAPITALIZATION_FOR_STANDALONE.
     * @param value The UDisplayContext value to set.
     * @param status Input/output status. If at entry this indicates a failure
     *               status, the function will do nothing; otherwise this will be
     *               updated with any new status from the function.
     * @stable ICU 53
     */
    virtual void setContext(UDisplayContext value, UErrorCode& status);

    /**
     * Get the formatter's UDisplayContext value for the specified UDisplayContextType,
     * such as UDISPCTX_TYPE_CAPITALIZATION.
     * @param type The UDisplayContextType whose value to return
     * @param status Input/output status. If at entry this indicates a failure
     *               status, the function will do nothing; otherwise this will be
     *               updated with any new status from the function.
     * @return The UDisplayContextValue for the specified type.
     * @stable ICU 53
     */
    virtual UDisplayContext getContext(UDisplayContextType type, UErrorCode& status) const;

    /**
     * Get the rounding mode. This will always return NumberFormat::ERoundingMode::kRoundUnnecessary
     * if the subclass does not support rounding. 
     * @return A rounding mode
     * @stable ICU 60
     */
    virtual ERoundingMode getRoundingMode() const;

    /**
     * Set the rounding mode. If a subclass does not support rounding, this will do nothing.
     * @param roundingMode A rounding mode
     * @stable ICU 60
     */
    virtual void setRoundingMode(ERoundingMode roundingMode);

public:

    /**
     * Return the class ID for this class.  This is useful for
     * comparing to a return value from getDynamicClassID(). Note that,
     * because NumberFormat is an abstract base class, no fully constructed object
     * will have the class ID returned by NumberFormat::getStaticClassID().
     * @return The class ID for all objects of this class.
     * @stable ICU 2.0
     */
    static UClassID U_EXPORT2 getStaticClassID();

    /**
     * Returns a unique class ID POLYMORPHICALLY.  Pure virtual override.
     * This method is to implement a simple version of RTTI, since not all
     * C++ compilers support genuine RTTI.  Polymorphic operator==() and
     * clone() methods call this method.
     * <P>
     * @return The class ID for this object. All objects of a
     * given class have the same class ID.  Objects of
     * other classes have different class IDs.
     * @stable ICU 2.0
     */
    virtual UClassID getDynamicClassID() const override = 0;

protected:

    /**
     * Default constructor for subclass use only.
     * @stable ICU 2.0
     */
    NumberFormat();

    /**
     * Copy constructor.
     * @stable ICU 2.0
     */
    NumberFormat(const NumberFormat&);

    /**
     * Assignment operator.
     * @stable ICU 2.0
     */
    NumberFormat& operator=(const NumberFormat&);

    /**
     * Returns the currency in effect for this formatter.  Subclasses
     * should override this method as needed.  Unlike getCurrency(),
     * this method should never return "".
     * @result output parameter for null-terminated result, which must
     * have a capacity of at least 4
     * @internal
     */
    virtual void getEffectiveCurrency(char16_t* result, UErrorCode& ec) const;

#ifndef U_HIDE_INTERNAL_API
    /**
     * Creates the specified number format style of the desired locale.
     * If mustBeDecimalFormat is true, then the returned pointer is
     * either a DecimalFormat or it is nullptr.
     * @internal
     */
    static NumberFormat* makeInstance(const Locale& desiredLocale,
                                      UNumberFormatStyle style,
                                      UBool mustBeDecimalFormat,
                                      UErrorCode& errorCode);
#endif  /* U_HIDE_INTERNAL_API */

private:

    static UBool isStyleSupported(UNumberFormatStyle style);

    /**
     * Creates the specified decimal format style of the desired locale.
     * @param desiredLocale    the given locale.
     * @param style            the given style.
     * @param errorCode        Output param filled with success/failure status.
     * @return                 A new NumberFormat instance.
     */
    static NumberFormat* makeInstance(const Locale& desiredLocale,
                                      UNumberFormatStyle style,
                                      UErrorCode& errorCode);

    UBool       fGroupingUsed;
    int32_t     fMaxIntegerDigits;
    int32_t     fMinIntegerDigits;
    int32_t     fMaxFractionDigits;
    int32_t     fMinFractionDigits;

  protected:
    /** \internal */
    static const int32_t gDefaultMaxIntegerDigits;
    /** \internal */
    static const int32_t gDefaultMinIntegerDigits;

  private:
    UBool      fParseIntegerOnly;
    UBool      fLenient; // true => lenient parse is enabled

    // ISO currency code
    char16_t      fCurrency[4];

    UDisplayContext fCapitalizationContext;

    friend class ICUNumberFormatFactory; // access to makeInstance
    friend class ICUNumberFormatService;
    friend class ::NumberFormatTest;  // access to isStyleSupported()
};

#if !UCONFIG_NO_SERVICE
/**
 * A NumberFormatFactory is used to register new number formats.  The factory
 * should be able to create any of the predefined formats for each locale it
 * supports.  When registered, the locales it supports extend or override the
 * locale already supported by ICU.
 *
 * @stable ICU 2.6
 */
class U_I18N_API NumberFormatFactory : public UObject {
public:

    /**
     * Destructor
     * @stable ICU 3.0
     */
    virtual ~NumberFormatFactory();

    /**
     * Return true if this factory will be visible.  Default is true.
     * If not visible, the locales supported by this factory will not
     * be listed by getAvailableLocales.
     * @stable ICU 2.6
     */
    virtual UBool visible() const = 0;

    /**
     * Return the locale names directly supported by this factory.  The number of names
     * is returned in count;
     * @stable ICU 2.6
     */
    virtual const UnicodeString * getSupportedIDs(int32_t &count, UErrorCode& status) const = 0;

    /**
     * Return a number format of the appropriate type.  If the locale
     * is not supported, return null.  If the locale is supported, but
     * the type is not provided by this service, return null.  Otherwise
     * return an appropriate instance of NumberFormat.
     * @stable ICU 2.6
     */
    virtual NumberFormat* createFormat(const Locale& loc, UNumberFormatStyle formatType) = 0;
};

/**
 * A NumberFormatFactory that supports a single locale.  It can be visible or invisible.
 * @stable ICU 2.6
 */
class U_I18N_API SimpleNumberFormatFactory : public NumberFormatFactory {
protected:
    /**
     * True if the locale supported by this factory is visible.
     * @stable ICU 2.6
     */
    const UBool _visible;

    /**
     * The locale supported by this factory, as a UnicodeString.
     * @stable ICU 2.6
     */
    UnicodeString _id;

public:
    /**
     * @stable ICU 2.6
     */
    SimpleNumberFormatFactory(const Locale& locale, UBool visible = true);

    /**
     * @stable ICU 3.0
     */
    virtual ~SimpleNumberFormatFactory();

    /**
     * @stable ICU 2.6
     */
    virtual UBool visible() const override;

    /**
     * @stable ICU 2.6
     */
    virtual const UnicodeString * getSupportedIDs(int32_t &count, UErrorCode& status) const override;
};
#endif /* #if !UCONFIG_NO_SERVICE */

// -------------------------------------

inline UBool
NumberFormat::isParseIntegerOnly() const
{
    return fParseIntegerOnly;
}

inline UBool
NumberFormat::isLenient() const
{
    return fLenient;
}

U_NAMESPACE_END

#endif /* #if !UCONFIG_NO_FORMATTING */

#endif /* U_SHOW_CPLUSPLUS_API */

#endif // _NUMFMT
//eof