/*
******************************************************************************
*   Copyright (C) 1997-2001, International Business Machines
*   Corporation and others.  All Rights Reserved.
******************************************************************************
*   file name:  nfsubs.cpp
*   encoding:   US-ASCII
*   tab size:   8 (not used)
*   indentation:4
*
* Modification history
* Date        Name      Comments
* 10/11/2001  Doug      Ported from ICU4J
*/

#include "nfsubs.h"

static const UChar gLessThan = 0x003c;
static const UChar gEquals = 0x003d;
static const UChar gGreaterThan = 0x003e;
static const UChar gPercent = 0x0025;
static const UChar gPound = 0x0023;
static const UChar gZero = 0x0030;
static const UChar gSpace = 0x0020;

static const UChar gEqualsEquals[] = 
{
    0x3D, 0x3D, 0
}; /* "==" */
static const UChar gGreaterGreaterGreaterThan[] = 
{
    0x3E, 0x3E, 0x3E, 0
}; /* ">>>" */
static const UChar gGreaterGreaterThan[] = 
{
    0x3E, 0x3E, 0
}; /* ">>" */

NFSubstitution*
NFSubstitution::makeSubstitution(int32_t pos,
                                 const NFRule* rule,
                                 const NFRule* predecessor,
                                 const NFRuleSet* ruleSet,
                                 const RuleBasedNumberFormat* formatter,
                                 const UnicodeString& description,
                                 UErrorCode& status) 
{
    // if the description is empty, return a NullSubstitution
    if (description.length() == 0) {
        return new NullSubstitution(pos, ruleSet, formatter, description, status);
    }

    switch (description.charAt(0)) {
        // if the description begins with '<'...
    case gLessThan:
        // throw an exception if the rule is a negative number
        // rule
        if (rule->getBaseValue() == NFRule::kNegativeNumberRule) {
            // throw new IllegalArgumentException("<< not allowed in negative-number rule");
            status = U_PARSE_ERROR;
            return NULL;
        }

        // if the rule is a fraction rule, return an
        // IntegralPartSubstitution
        else if (rule->getBaseValue() == NFRule::kImproperFractionRule
            || rule->getBaseValue() == NFRule::kProperFractionRule
            || rule->getBaseValue() == NFRule::kMasterRule) {
            return new IntegralPartSubstitution(pos, ruleSet, formatter, description, status);
        }

        // if the rule set containing the rule is a fraction
        // rule set, return a NumeratorSubstitution
        else if (ruleSet->isFractionRuleSet()) {
            return new NumeratorSubstitution(pos, rule->getBaseValue().asDouble(),
                formatter->getDefaultRuleSet(), formatter, description, status);
        }

        // otherwise, return a MultiplierSubstitution
        else {
            return new MultiplierSubstitution(pos, rule->getDivisor(), ruleSet,
                formatter, description, status);
        }

        // if the description begins with '>'...
    case gGreaterThan:
        // if the rule is a negative-number rule, return
        // an AbsoluteValueSubstitution
        if (rule->getBaseValue() == NFRule::kNegativeNumberRule) {
            return new AbsoluteValueSubstitution(pos, ruleSet, formatter, description, status);
        }
        
        // if the rule is a fraction rule, return a
        // FractionalPartSubstitution
        else if (rule->getBaseValue() == NFRule::kImproperFractionRule
            || rule->getBaseValue() == NFRule::kProperFractionRule
            || rule->getBaseValue() == NFRule::kMasterRule) {
            return new FractionalPartSubstitution(pos, ruleSet, formatter, description, status);
        }
        
        // if the rule set owning the rule is a fraction rule set,
        // throw an exception
        else if (ruleSet->isFractionRuleSet()) {
            // throw new IllegalArgumentException(">> not allowed in fraction rule set");
            status = U_PARSE_ERROR;
            return NULL;
        }

        // otherwise, return a ModulusSubstitution
        else {
            return new ModulusSubstitution(pos, rule->getDivisor(), predecessor,
                ruleSet, formatter, description, status);
        }

        // if the description begins with '=', always return a
        // SameValueSubstitution
    case gEquals:
        return new SameValueSubstitution(pos, ruleSet, formatter, description, status);

        // and if it's anything else, throw an exception
    default:
        // throw new IllegalArgumentException("Illegal substitution character");
        status = U_PARSE_ERROR;
    }
    return NULL;
}

NFSubstitution::NFSubstitution(int32_t _pos,
                               const NFRuleSet* _ruleSet,
                               const RuleBasedNumberFormat* formatter,
                               const UnicodeString& description,
                               UErrorCode& status)
: pos(_pos), ruleSet(NULL), numberFormat(NULL)
{
    // the description should begin and end with the same character.
    // If it doesn't that's a syntax error.  Otherwise,
    // makeSubstitution() was the only thing that needed to know
    // about these characters, so strip them off
    UnicodeString workingDescription(description);
    if (description.length() >= 2 && description.charAt(0) == description.charAt(
        description.length() - 1)) {
        workingDescription.remove(description.length() - 1, 1);
        workingDescription.remove(0, 1);
    }
    else if (description.length() != 0) {
        // throw new IllegalArgumentException("Illegal substitution syntax");
        status = U_PARSE_ERROR;
        return;
    }

    // if the description was just two paired token characters
    // (i.e., "<<" or ">>"), it uses the rule set it belongs to to
    // format its result
    if (workingDescription.length() == 0) {
        this->ruleSet = _ruleSet;
    }
    // if the description contains a rule set name, that's the rule
    // set we use to format the result: get a reference to the
    // names rule set
    else if (workingDescription.charAt(0) == gPercent) {
        this->ruleSet = formatter->findRuleSet(workingDescription, status);
    }
    // if the description begins with 0 or #, treat it as a
    // DecimalFormat pattern, and initialize a DecimalFormat with
    // that pattern (then set it to use the DecimalFormatSymbols
    // belonging to our formatter)
    else if (workingDescription.charAt(0) == gPound || workingDescription.charAt(0) ==gZero) {
        this->numberFormat = new DecimalFormat(workingDescription, *(formatter->getDecimalFormatSymbols()), status);
        // this->numberFormat->setDecimalFormatSymbols(formatter->getDecimalFormatSymbols());
    }
    // if the description is ">>>", this substitution bypasses the
    // usual rule-search process and always uses the rule that precedes
    // it in its own rule set's rule list (this is used for place-value
    // notations: formats where you want to see a particular part of
    // a number even when it's 0)
    else if (workingDescription.charAt(0) == gGreaterThan) {
        // this causes problems when >>> is used in a frationalPartSubstitution
        // this->ruleSet = NULL;
        this->ruleSet = _ruleSet;
        this->numberFormat = NULL;
    }
    // and of the description is none of these things, it's a syntax error
    else {
        // throw new IllegalArgumentException("Illegal substitution syntax");
        status = U_PARSE_ERROR;
    }
}

NFSubstitution::~NFSubstitution()
{
    // cast away const
    delete (NumberFormat*)numberFormat; numberFormat = NULL;
}

/**
 * Set's the substitution's divisor.  Used by NFRule.setBaseValue().
 * A no-op for all substitutions except multiplier and modulus
 * substitutions.
 * @param radix The radix of the divisor
 * @param exponent The exponent of the divisor
 */
void
NFSubstitution::setDivisor(int32_t /*radix*/, int32_t /*exponent*/) {
    // a no-op for all substitutions except multiplier and modulus substitutions
}


    //-----------------------------------------------------------------------
    // boilerplate
    //-----------------------------------------------------------------------

const char NFSubstitution::fgClassID = 0;

UClassID
NFSubstitution::getDynamicClassID() const {
    return getStaticClassID();
}


    /**
     * Compares two substitutions for equality
     * @param The substitution to compare this one to
     * @return true if the two substitutions are functionally equivalent
     */
UBool 
NFSubstitution::operator==(const NFSubstitution& rhs) const
{
    // compare class and all of the fields all substitutions have
    // in common
    // this should be called by subclasses before their own equality tests
    return getDynamicClassID() == rhs.getDynamicClassID() 
        && pos == rhs.pos
        && ruleSet == rhs.ruleSet
        && *numberFormat == *rhs.numberFormat;
}

    /**
     * Returns a textual description of the substitution
     * @return A textual description of the substitution.  This might
     * not be identical to the description it was created from, but
     * it'll produce the same result.
     */
void 
NFSubstitution::toString(UnicodeString& text) const
{
    // use tokenChar() to get the character at the beginning and
    // end of the substitutin token.  In between them will go
    // either the name of the rule set it uses, or the pattern of
    // the DecimalFormat it uses
    text.remove();
    text.append(tokenChar());

    UnicodeString temp;
    if (ruleSet != NULL) {
        ruleSet->getName(temp);
    } else {
        numberFormat->toPattern(temp);
    }
    text.append(temp);
    text.append(tokenChar());
}

//-----------------------------------------------------------------------
// formatting
//-----------------------------------------------------------------------

/**
 * Performs a mathematical operation on the number, formats it using
 * either ruleSet or decimalFormat, and inserts the result into
 * toInsertInto.
 * @param number The number being formatted.
 * @param toInsertInto The string we insert the result into
 * @param pos The position in toInsertInto where the owning rule's
 * rule text begins (this value is added to this substitution's
 * position to determine exactly where to insert the new text)
 */
void
NFSubstitution::doSubstitution(const llong &number, UnicodeString& toInsertInto, int32_t _pos) const
{
    if (ruleSet != NULL) {
        // perform a transformation on the number that is dependent
        // on the type of substitution this is, then just call its
        // rule set's format() method to format the result
        ruleSet->format(transformNumber(number), toInsertInto, _pos + this->pos);
    } else {
        // or perform the transformation on the number (preserving
        // the result's fractional part if the formatter it set
        // to show it), then use that formatter's format() method
        // to format the result
        double numberToFormat = transformNumber(number.asDouble());
        if (numberFormat->getMaximumFractionDigits() == 0) {
            numberToFormat = uprv_floor(numberToFormat);
        }

        UnicodeString temp;
        numberFormat->format(numberToFormat, temp);
        toInsertInto.insert(_pos + this->pos, temp);
    }
}

/**
 * Performs a mathematical operation on the number, formats it using
 * either ruleSet or decimalFormat, and inserts the result into
 * toInsertInto.
 * @param number The number being formatted.
 * @param toInsertInto The string we insert the result into
 * @param pos The position in toInsertInto where the owning rule's
 * rule text begins (this value is added to this substitution's
 * position to determine exactly where to insert the new text)
 */
void 
NFSubstitution::doSubstitution(double number, UnicodeString& toInsertInto, int32_t _pos) const {
    // perform a transformation on the number being formatted that
    // is dependent on the type of substitution this is
    double numberToFormat = transformNumber(number);

    // if the result is an integer, from here on out we work in integer
    // space (saving time and memory and preserving accuracy)
    if (numberToFormat == uprv_floor(numberToFormat) && ruleSet != NULL) {
        ruleSet->format(llong(numberToFormat), toInsertInto, _pos + this->pos);

        // if the result isn't an integer, then call either our rule set's
        // format() method or our DecimalFormat's format() method to
        // format the result
    } else {
        if (ruleSet != NULL) {
            ruleSet->format(numberToFormat, toInsertInto, _pos + this->pos);
        } else {
            UnicodeString temp;
            numberFormat->format(numberToFormat, temp);
            toInsertInto.insert(_pos + this->pos, temp);
        }
    }
}


    //-----------------------------------------------------------------------
    // parsing
    //-----------------------------------------------------------------------

#ifdef RBNF_DEBUG
#include <stdio.h>
#endif

/**
 * Parses a string using the rule set or DecimalFormat belonging
 * to this substitution.  If there's a match, a mathematical
 * operation (the inverse of the one used in formatting) is
 * performed on the result of the parse and the value passed in
 * and returned as the result.  The parse position is updated to
 * point to the first unmatched character in the string.
 * @param text The string to parse
 * @param parsePosition On entry, ignored, but assumed to be 0.
 * On exit, this is updated to point to the first unmatched
 * character (or 0 if the substitution didn't match)
 * @param baseValue A partial parse result that should be
 * combined with the result of this parse
 * @param upperBound When searching the rule set for a rule
 * matching the string passed in, only rules with base values
 * lower than this are considered
 * @param lenientParse If true and matching against rules fails,
 * the substitution will also try matching the text against
 * numerals using a default-costructed NumberFormat.  If false,
 * no extra work is done.  (This value is false whenever the
 * formatter isn't in lenient-parse mode, but is also false
 * under some conditions even when the formatter _is_ in
 * lenient-parse mode.)
 * @return If there's a match, this is the result of composing
 * baseValue with whatever was returned from matching the
 * characters.  This will be either a Long or a Double.  If there's
 * no match this is new Long(0) (not null), and parsePosition
 * is left unchanged.
 */
UBool 
NFSubstitution::doParse(const UnicodeString& text, 
                        ParsePosition& parsePosition, 
                        double baseValue,
                        double upperBound, 
                        UBool lenientParse,
                        Formattable& result) const
{
#ifdef RBNF_DEBUG
    fprintf(stderr, "<nfsubs> %x bv: %g ub: %g\n", this, baseValue, upperBound);
#endif
    // figure out the highest base value a rule can have and match
    // the text being parsed (this varies according to the type of
    // substitutions: multiplier, modulus, and numerator substitutions
    // restrict the search to rules with base values lower than their
    // own; same-value substitutions leave the upper bound wherever
    // it was, and the others allow any rule to match
    upperBound = calcUpperBound(upperBound);

    // use our rule set to parse the text.  If that fails and
    // lenient parsing is enabled (this is always false if the
    // formatter's lenient-parsing mode is off, but it may also
    // be false even when the formatter's lenient-parse mode is
    // on), then also try parsing the text using a default-
    // constructed NumberFormat
    if (ruleSet != NULL) {
        ruleSet->parse(text, parsePosition, upperBound, result);
        if (lenientParse && !ruleSet->isFractionRuleSet() && parsePosition.getIndex() == 0) {
            UErrorCode status = U_ZERO_ERROR;
            NumberFormat* fmt = NumberFormat::createInstance(status);
            if (U_SUCCESS(status)) {
                fmt->parse(text, result, parsePosition);
            }
            delete fmt;
        }

        // ...or use our DecimalFormat to parse the text
    } else {
        numberFormat->parse(text, result, parsePosition);
    }

    // if the parse was successful, we've already advanced the caller's
    // parse position (this is the one function that doesn't have one
    // of its own).  Derive a parse result and return it as a Long,
    // if possible, or a Double
    if (parsePosition.getIndex() != 0) {
        double tempResult = (result.getType() == Formattable::kLong) ? 
            (double)result.getLong() : 
        result.getDouble();

        // composeRuleValue() produces a full parse result from
        // the partial parse result passed to this function from
        // the caller (this is either the owning rule's base value
        // or the partial result obtained from composing the
        // owning rule's base value with its other substitution's
        // parse result) and the partial parse result obtained by
        // matching the substitution (which will be the same value
        // the caller would get by parsing just this part of the
        // text with RuleBasedNumberFormat.parse() ).  How the two
        // values are used to derive the full parse result depends
        // on the types of substitutions: For a regular rule, the
        // ultimate result is its multiplier substitution's result
        // times the rule's divisor (or the rule's base value) plus
        // the modulus substitution's result (which will actually
        // supersede part of the rule's base value).  For a negative-
        // number rule, the result is the negative of its substitution's
        // result.  For a fraction rule, it's the sum of its two
        // substitution results.  For a rule in a fraction rule set,
        // it's the numerator substitution's result divided by
        // the rule's base value.  Results from same-value substitutions
        // propagate back upard, and null substitutions don't affect
        // the result.
        tempResult = composeRuleValue(tempResult, baseValue);
        result.setDouble(tempResult);
        return TRUE;
        // if the parse was UNsuccessful, return 0
    } else {
        result.setLong(0);
        return FALSE;
    }
}


UBool 
NFSubstitution::isNullSubstitution() const {
    return FALSE;
}

    /**
     * Returns true if this is a modulus substitution.  (We didn't do this
     * with instanceof partially because it causes source files to
     * proliferate and partially because we have to port this to C++.)
     * @return true if this object is an instance of ModulusSubstitution
     */
UBool 
NFSubstitution::isModulusSubstitution() const {
    return FALSE;
}

//===================================================================
// SameValueSubstitution
//===================================================================

/**
 * A substitution that passes the value passed to it through unchanged.
 * Represented by == in rule descriptions.
 */
SameValueSubstitution::SameValueSubstitution(int32_t _pos,
                        const NFRuleSet* _ruleSet,
                        const RuleBasedNumberFormat* formatter,
                        const UnicodeString& description,
                        UErrorCode& status) 
: NFSubstitution(_pos, _ruleSet, formatter, description, status)
{
    if (description == gEqualsEquals) {
        // throw new IllegalArgumentException("== is not a legal token");
        status = U_PARSE_ERROR;
    }
}

const char SameValueSubstitution::fgClassID = 0;

UClassID
SameValueSubstitution::getDynamicClassID() const {
    return getStaticClassID();
}


//===================================================================
// MultiplierSubstitution
//===================================================================

const char MultiplierSubstitution::fgClassID = 0;

UClassID
MultiplierSubstitution::getDynamicClassID() const {
    return getStaticClassID();
}

UBool MultiplierSubstitution::operator==(const NFSubstitution& rhs) const
{
    return NFSubstitution::operator==(rhs) &&
        divisor == ((const MultiplierSubstitution*)&rhs)->divisor;
}


//===================================================================
// ModulusSubstitution
//===================================================================

/**
 * A substitution that divides the number being formatted by the its rule's
 * divisor and formats the remainder.  Represented by "&gt;&gt;" in a
 * regular rule.
 */
ModulusSubstitution::ModulusSubstitution(int32_t _pos,
                                         double _divisor,
                                         const NFRule* predecessor,
                                         const NFRuleSet* _ruleSet,
                                         const RuleBasedNumberFormat* formatter,
                                         const UnicodeString& description,
                                         UErrorCode& status)
 : NFSubstitution(_pos, _ruleSet, formatter, description, status)
 , divisor(_divisor)
 , ruleToUse(NULL)
{
    ldivisor = _divisor;

    // the owning rule's divisor controls the behavior of this
    // substitution: rather than keeping a backpointer to the rule,
    // we keep a copy of the divisor

    if (description == gGreaterGreaterGreaterThan) {
        // the >>> token doesn't alter how this substituion calculates the
        // values it uses for formatting and parsing, but it changes
        // what's done with that value after it's obtained: >>> short-
        // circuits the rule-search process and goes straight to the
        // specified rule to format the substitution value
        ruleToUse = predecessor;
    }
}

const char ModulusSubstitution::fgClassID = 0;

UClassID
ModulusSubstitution::getDynamicClassID() const {
    return getStaticClassID();
}

UBool ModulusSubstitution::operator==(const NFSubstitution& rhs) const
{
    return NFSubstitution::operator==(rhs) &&
        divisor == ((const ModulusSubstitution*)&rhs)->divisor &&
        ruleToUse == ((const ModulusSubstitution*)&rhs)->ruleToUse;
}

//-----------------------------------------------------------------------
// formatting
//-----------------------------------------------------------------------

/**
 * If this is a &gt;&gt;&gt; substitution, use ruleToUse to fill in
 * the substitution.  Otherwise, just use the superclass function.
 * @param number The number being formatted
 * @toInsertInto The string to insert the result of this substitution
 * into
 * @param pos The position of the rule text in toInsertInto
 */
void
ModulusSubstitution::doSubstitution(const llong &   number, UnicodeString& toInsertInto, int32_t _pos) const
{
    // if this isn't a >>> substitution, just use the inherited version
    // of this function (which uses either a rule set or a DecimalFormat
    // to format its substitution value)
    if (ruleToUse == NULL) {
        NFSubstitution::doSubstitution(number, toInsertInto, _pos);
        
        // a >>> substitution goes straight to a particular rule to
        // format the substitution value
    } else {
        llong numberToFormat = transformNumber(number);
        ruleToUse->doFormat(numberToFormat, toInsertInto, _pos + getPos());
    }
}

/**
* If this is a &gt;&gt;&gt; substitution, use ruleToUse to fill in
* the substitution.  Otherwise, just use the superclass function.
* @param number The number being formatted
* @toInsertInto The string to insert the result of this substitution
* into
* @param pos The position of the rule text in toInsertInto
*/
void 
ModulusSubstitution::doSubstitution(double number, UnicodeString& toInsertInto, int32_t _pos) const
{
    // if this isn't a >>> substitution, just use the inherited version
    // of this function (which uses either a rule set or a DecimalFormat
    // to format its substitution value)
    if (ruleToUse == NULL) {
        NFSubstitution::doSubstitution(number, toInsertInto, _pos);
        
        // a >>> substitution goes straight to a particular rule to
        // format the substitution value
    } else {
        double numberToFormat = transformNumber(number);
        
        ruleToUse->doFormat(numberToFormat, toInsertInto, _pos + getPos());
    }
}


//-----------------------------------------------------------------------
// parsing
//-----------------------------------------------------------------------

/**
 * If this is a &gt;&gt;&gt; substitution, match only against ruleToUse.
 * Otherwise, use the superclass function.
 * @param text The string to parse
 * @param parsePosition Ignored on entry, updated on exit to point to
 * the first unmatched character.
 * @param baseValue The partial parse result prior to calling this
 * routine.
 */
UBool 
ModulusSubstitution::doParse(const UnicodeString& text, 
                             ParsePosition& parsePosition,
                             double baseValue,
                             double upperBound,
                             UBool lenientParse,
                             Formattable& result) const
{
    // if this isn't a >>> substitution, we can just use the
    // inherited parse() routine to do the parsing
    if (ruleToUse == NULL) {
        return NFSubstitution::doParse(text, parsePosition, baseValue, upperBound, lenientParse, result);

        // but if it IS a >>> substitution, we have to do it here: we
        // use the specific rule's doParse() method, and then we have to
        // do some of the other work of NFRuleSet.parse()
    } else {
        ruleToUse->doParse(text, parsePosition, FALSE, upperBound, result);

        if (parsePosition.getIndex() != 0) {
            double tempResult = result.getDouble();
            tempResult = composeRuleValue(tempResult, baseValue);
            result.setDouble(tempResult);
        }

        return TRUE;
    }
}


//===================================================================
// IntegralPartSubstitution
//===================================================================

const char IntegralPartSubstitution::fgClassID = 0;

UClassID
IntegralPartSubstitution::getDynamicClassID() const {
    return getStaticClassID();
}


//===================================================================
// FractionalPartSubstitution
//===================================================================


    /**
     * Constructs a FractionalPartSubstitution.  This object keeps a flag
     * telling whether it should format by digits or not.  In addition,
     * it marks the rule set it calls (if any) as a fraction rule set.
     */
FractionalPartSubstitution::FractionalPartSubstitution(int32_t _pos,
                             const NFRuleSet* _ruleSet,
                             const RuleBasedNumberFormat* formatter,
                             const UnicodeString& description,
                             UErrorCode& status)
 : NFSubstitution(_pos, _ruleSet, formatter, description, status)
 , byDigits(FALSE)
 , useSpaces(TRUE)

{
    // akk, ruleSet can change in superclass constructor
    if (description == gGreaterGreaterThan ||
        description == gGreaterGreaterGreaterThan ||
        _ruleSet == getRuleSet()) {
        byDigits = TRUE;
        if (description == gGreaterGreaterGreaterThan) {
            useSpaces = FALSE;
        }
    } else {
        // cast away const
        ((NFRuleSet*)getRuleSet())->makeIntoFractionRuleSet();
    }
    
    // TODO: Thai doesn't use spaces, so spelling out decimals with 
    // spaces between the words for each digit is incorrect.
    // The rules don't seem to accomodate this, at least I can't figure 
    // out how to handle it using the rules.  Need to provide better
    // control over fractional part formatting.  
    // For now, just check if locale uses the Thai language.
    
    // useSpaces = strcmp(formatter->locale.getLanguage(), "th") != 0;
}

//-----------------------------------------------------------------------
// formatting
//-----------------------------------------------------------------------

/**
 * If in "by digits" mode, fills in the substitution one decimal digit
 * at a time using the rule set containing this substitution.
 * Otherwise, uses the superclass function.
 * @param number The number being formatted
 * @param toInsertInto The string to insert the result of formatting
 * the substitution into
 * @param pos The position of the owning rule's rule text in
 * toInsertInto
 */
void 
FractionalPartSubstitution::doSubstitution(double number, UnicodeString& toInsertInto, int32_t _pos) const
{
    // if we're not in "byDigits" mode, just use the inherited
    // doSubstitution() routine
    if (!byDigits) {
        NFSubstitution::doSubstitution(number, toInsertInto, _pos);
        
        // if we're in "byDigits" mode, transform the value into an integer
        // by moving the decimal point eight places to the right and
        // pulling digits off the right one at a time, formatting each digit
        // as an integer using this substitution's owning rule set
        // (this is slower, but more accurate, than doing it from the
        // other end)
    } else {
        int32_t numberToFormat = (int32_t)uprv_round(transformNumber(number) * uprv_pow(10, kMaxDecimalDigits));
        // this flag keeps us from formatting trailing zeros.  It starts
        // out false because we're pulling from the right, and switches
        // to true the first time we encounter a non-zero digit
        UBool doZeros = FALSE;
        for (int32_t i = 0; i < kMaxDecimalDigits; i++) {
            int32_t digit = numberToFormat % 10;
            if (digit != 0 || doZeros) {
                if (doZeros && useSpaces) {
                    toInsertInto.insert(_pos + getPos(), gSpace);
                }
                doZeros = TRUE;
                getRuleSet()->format(digit, toInsertInto, _pos + getPos());
            }
            numberToFormat /= 10;
        }
    }
}

//-----------------------------------------------------------------------
// parsing
//-----------------------------------------------------------------------

/**
 * If in "by digits" mode, parses the string as if it were a string
 * of individual digits; otherwise, uses the superclass function.
 * @param text The string to parse
 * @param parsePosition Ignored on entry, but updated on exit to point
 * to the first unmatched character
 * @param baseValue The partial parse result prior to entering this
 * function
 * @param upperBound Only consider rules with base values lower than
 * this when filling in the substitution
 * @param lenientParse If true, try matching the text as numerals if
 * matching as words doesn't work
 * @return If the match was successful, the current partial parse
 * result; otherwise new Long(0).  The result is either a Long or
 * a Double.
 */
UBool
FractionalPartSubstitution::doParse(const UnicodeString& text,
                ParsePosition& parsePosition,
                double baseValue,
                double /*upperBound*/,
                UBool lenientParse,
                Formattable& resVal) const
{
    // if we're not in byDigits mode, we can just use the inherited
    // doParse()
    if (!byDigits) {
        return NFSubstitution::doParse(text, parsePosition, baseValue, 0, lenientParse, resVal);

        // if we ARE in byDigits mode, parse the text one digit at a time
        // using this substitution's owning rule set (we do this by setting
        // upperBound to 10 when calling doParse() ) until we reach
        // nonmatching text
    } else {
        UnicodeString workText(text);
        ParsePosition workPos(1);
        double result = 0;
        int32_t digit;
        double p10 = 0.1;

        NumberFormat* fmt = NULL;
        while (workText.length() > 0 && workPos.getIndex() != 0) {
            workPos.setIndex(0);
            Formattable temp;
            getRuleSet()->parse(workText, workPos, 10, temp);
            digit = temp.getType() == Formattable::kLong ?
                temp.getLong() :
            (int32_t)temp.getDouble();
            
            if (lenientParse && workPos.getIndex() == 0) {
                if (!fmt) {
                    UErrorCode status = U_ZERO_ERROR;
                    fmt = NumberFormat::createInstance(status);
                    if (U_FAILURE(status)) {
                        delete fmt;
                        fmt = NULL;
                    }
                }
                if (fmt) {
                    fmt->parse(workText, temp, workPos);
                    digit = temp.getLong();
                }
            }

            if (workPos.getIndex() != 0) {
                result += digit * p10;
                p10 /= 10;
                parsePosition.setIndex(parsePosition.getIndex() + workPos.getIndex());
                workText.removeBetween(0, workPos.getIndex());
                while (workText.length() > 0 && workText.charAt(0) == gSpace) {
                    workText.removeBetween(0, 1);
                    parsePosition.setIndex(parsePosition.getIndex() + 1);
                }
            }
        }
        delete fmt;

        result = composeRuleValue(result, baseValue);
        resVal.setDouble(result);
        return TRUE;
    }
}

UBool 
FractionalPartSubstitution::operator==(const NFSubstitution& rhs) const
{
    return NFSubstitution::operator==(rhs) &&
        ((const FractionalPartSubstitution*)&rhs)->byDigits == byDigits;
}

const char FractionalPartSubstitution::fgClassID = 0;

UClassID
FractionalPartSubstitution::getDynamicClassID() const {
    return getStaticClassID();
}


//===================================================================
// AbsoluteValueSubstitution
//===================================================================

const char AbsoluteValueSubstitution::fgClassID = 0;

UClassID
AbsoluteValueSubstitution::getDynamicClassID() const {
    return getStaticClassID();
}

//===================================================================
// NumeratorSubstitution
//===================================================================

UBool 
NumeratorSubstitution::operator==(const NFSubstitution& rhs) const
{
    return NFSubstitution::operator==(rhs) &&
        denominator == ((const NumeratorSubstitution*)&rhs)->denominator;
}

const char NumeratorSubstitution::fgClassID = 0;

UClassID
NumeratorSubstitution::getDynamicClassID() const {
    return getStaticClassID();
}

//===================================================================
// NullSubstitution
//===================================================================

const char NullSubstitution::fgClassID = 0;

UClassID
NullSubstitution::getDynamicClassID() const {
    return getStaticClassID();
}