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RuleBasedNumberFormat Class Reference

#include <rbnf.h>

Inheritance diagram for RuleBasedNumberFormat:

NumberFormat Format UObject UMemory

List of all members.


Detailed Description

The RuleBasedNumberFormat class formats numbers according to a set of rules. This number formatter is typically used for spelling out numeric values in words (e.g., 25,3476 as "twenty-five thousand three hundred seventy-six" or "vingt-cinq mille trois cents soixante-seize" or "fünfundzwanzigtausenddreihundertsechsundsiebzig"), but can also be used for other complicated formatting tasks, such as formatting a number of seconds as hours, minutes and seconds (e.g., 3,730 as "1:02:10").

The resources contain three predefined formatters for each locale: spellout, which spells out a value in words (123 is "one hundred twenty-three"); ordinal, which appends an ordinal suffix to the end of a numeral (123 is "123rd"); and duration, which shows a duration in seconds as hours, minutes, and seconds (123 is "2:03").  The client can also define more specialized RuleBasedNumberFormats by supplying programmer-defined rule sets.

The behavior of a RuleBasedNumberFormat is specified by a textual description that is either passed to the constructor as a String or loaded from a resource bundle. In its simplest form, the description consists of a semicolon-delimited list of rules. Each rule has a string of output text and a value or range of values it is applicable to. In a typical spellout rule set, the first twenty rules are the words for the numbers from 0 to 19:

zero; one; two; three; four; five; six; seven; eight; nine;
 ten; eleven; twelve; thirteen; fourteen; fifteen; sixteen; seventeen; eighteen; nineteen;

For larger numbers, we can use the preceding set of rules to format the ones place, and we only have to supply the words for the multiples of 10:

 20: twenty[->>];
 30: thirty[->>];
 40: forty[->>];
 50: fifty[->>];
 60: sixty[->>];
 70: seventy[->>];
 80: eighty[->>];
 90: ninety[->>];

In these rules, the base value is spelled out explicitly and set off from the rule's output text with a colon. The rules are in a sorted list, and a rule is applicable to all numbers from its own base value to one less than the next rule's base value. The ">>" token is called a substitution and tells the fomatter to isolate the number's ones digit, format it using this same set of rules, and place the result at the position of the ">>" token. Text in brackets is omitted if the number being formatted is an even multiple of 10 (the hyphen is a literal hyphen; 24 is "twenty-four," not "twenty four").

For even larger numbers, we can actually look up several parts of the number in the list:

100: << hundred[ >>];

The "<<" represents a new kind of substitution. The << isolates the hundreds digit (and any digits to its left), formats it using this same rule set, and places the result where the "<<" was. Notice also that the meaning of >> has changed: it now refers to both the tens and the ones digits. The meaning of both substitutions depends on the rule's base value. The base value determines the rule's divisor, which is the highest power of 10 that is less than or equal to the base value (the user can change this). To fill in the substitutions, the formatter divides the number being formatted by the divisor. The integral quotient is used to fill in the << substitution, and the remainder is used to fill in the >> substitution. The meaning of the brackets changes similarly: text in brackets is omitted if the value being formatted is an even multiple of the rule's divisor. The rules are applied recursively, so if a substitution is filled in with text that includes another substitution, that substitution is also filled in.

This rule covers values up to 999, at which point we add another rule:

1000: << thousand[ >>];

Again, the meanings of the brackets and substitution tokens shift because the rule's base value is a higher power of 10, changing the rule's divisor. This rule can actually be used all the way up to 999,999. This allows us to finish out the rules as follows:

 1,000,000: << million[ >>];
 1,000,000,000: << billion[ >>];
 1,000,000,000,000: << trillion[ >>];
 1,000,000,000,000,000: OUT OF RANGE!;

Commas, periods, and spaces can be used in the base values to improve legibility and are ignored by the rule parser. The last rule in the list is customarily treated as an "overflow rule," applying to everything from its base value on up, and often (as in this example) being used to print out an error message or default representation. Notice also that the size of the major groupings in large numbers is controlled by the spacing of the rules: because in English we group numbers by thousand, the higher rules are separated from each other by a factor of 1,000.

To see how these rules actually work in practice, consider the following example: Formatting 25,430 with this rule set would work like this:

<< thousand >> [the rule whose base value is 1,000 is applicable to 25,340]
twenty->> thousand >> [25,340 over 1,000 is 25. The rule for 20 applies.]
twenty-five thousand >> [25 mod 10 is 5. The rule for 5 is "five."
twenty-five thousand << hundred >> [25,340 mod 1,000 is 340. The rule for 100 applies.]
twenty-five thousand three hundred >> [340 over 100 is 3. The rule for 3 is "three."]
twenty-five thousand three hundred forty [340 mod 100 is 40. The rule for 40 applies. Since 40 divides evenly by 10, the hyphen and substitution in the brackets are omitted.]

The above syntax suffices only to format positive integers. To format negative numbers, we add a special rule:

-x: minus >>;

This is called a negative-number rule, and is identified by "-x" where the base value would be. This rule is used to format all negative numbers. the >> token here means "find the number's absolute value, format it with these rules, and put the result here."

We also add a special rule called a fraction rule for numbers with fractional parts:

x.x: << point >>;

This rule is used for all positive non-integers (negative non-integers pass through the negative-number rule first and then through this rule). Here, the << token refers to the number's integral part, and the >> to the number's fractional part. The fractional part is formatted as a series of single-digit numbers (e.g., 123.456 would be formatted as "one hundred twenty-three point four five six").

To see how this rule syntax is applied to various languages, examine the resource data.

There is actually much more flexibility built into the rule language than the description above shows. A formatter may own multiple rule sets, which can be selected by the caller, and which can use each other to fill in their substitutions. Substitutions can also be filled in with digits, using a DecimalFormat object. There is syntax that can be used to alter a rule's divisor in various ways. And there is provision for much more flexible fraction handling. A complete description of the rule syntax follows:


The description of a RuleBasedNumberFormat's behavior consists of one or more rule sets. Each rule set consists of a name, a colon, and a list of rules. A rule set name must begin with a % sign. Rule sets with names that begin with a single % sign are public: the caller can specify that they be used to format and parse numbers. Rule sets with names that begin with %% are private: they exist only for the use of other rule sets. If a formatter only has one rule set, the name may be omitted.

The user can also specify a special "rule set" named %lenient-parse. The body of %lenient-parse isn't a set of number-formatting rules, but a RuleBasedCollator description which is used to define equivalences for lenient parsing. For more information on the syntax, see RuleBasedCollator. For more information on lenient parsing, see setLenientParse(). Note: symbols that have syntactic meaning in collation rules, such as '&', have no particular meaning when appearing outside of the lenient-parse rule set.

The body of a rule set consists of an ordered, semicolon-delimited list of rules. Internally, every rule has a base value, a divisor, rule text, and zero, one, or two substitutions. These parameters are controlled by the description syntax, which consists of a rule descriptor, a colon, and a rule body.

A rule descriptor can take one of the following forms (text in italics is the name of a token):

bv: bv specifies the rule's base value. bv is a decimal number expressed using ASCII digits. bv may contain spaces, period, and commas, which are ignored. The rule's divisor is the highest power of 10 less than or equal to the base value.
bv/rad: bv specifies the rule's base value. The rule's divisor is the highest power of rad less than or equal to the base value.
bv>: bv specifies the rule's base value. To calculate the divisor, let the radix be 10, and the exponent be the highest exponent of the radix that yields a result less than or equal to the base value. Every > character after the base value decreases the exponent by 1. If the exponent is positive or 0, the divisor is the radix raised to the power of the exponent; otherwise, the divisor is 1.
bv/rad>: bv specifies the rule's base value. To calculate the divisor, let the radix be rad, and the exponent be the highest exponent of the radix that yields a result less than or equal to the base value. Every > character after the radix decreases the exponent by 1. If the exponent is positive or 0, the divisor is the radix raised to the power of the exponent; otherwise, the divisor is 1.
-x: The rule is a negative-number rule.
x.x: The rule is an improper fraction rule.
0.x: The rule is a proper fraction rule.
x.0: The rule is a master rule.
nothing If the rule's rule descriptor is left out, the base value is one plus the preceding rule's base value (or zero if this is the first rule in the list) in a normal rule set.  In a fraction rule set, the base value is the same as the preceding rule's base value.

A rule set may be either a regular rule set or a fraction rule set, depending on whether it is used to format a number's integral part (or the whole number) or a number's fractional part. Using a rule set to format a rule's fractional part makes it a fraction rule set.

Which rule is used to format a number is defined according to one of the following algorithms: If the rule set is a regular rule set, do the following:

If the rule set is a fraction rule set, do the following:

A rule's body consists of a string of characters terminated by a semicolon. The rule may include zero, one, or two substitution tokens, and a range of text in brackets. The brackets denote optional text (and may also include one or both substitutions). The exact meanings of the substitution tokens, and under what conditions optional text is omitted, depend on the syntax of the substitution token and the context. The rest of the text in a rule body is literal text that is output when the rule matches the number being formatted.

A substitution token begins and ends with a token character. The token character and the context together specify a mathematical operation to be performed on the number being formatted. An optional substitution descriptor specifies how the value resulting from that operation is used to fill in the substitution. The position of the substitution token in the rule body specifies the location of the resultant text in the original rule text.

The meanings of the substitution token characters are as follows:

>> in normal rule Divide the number by the rule's divisor and format the remainder
in negative-number rule Find the absolute value of the number and format the result
in fraction or master rule Isolate the number's fractional part and format it.
in rule in fraction rule set Not allowed.
>>> in normal rule Divide the number by the rule's divisor and format the remainder, but bypass the normal rule-selection process and just use the rule that precedes this one in this rule list.
in all other rules Not allowed.
<< in normal rule Divide the number by the rule's divisor and format the quotient
in negative-number rule Not allowed.
in fraction or master rule Isolate the number's integral part and format it.
in rule in fraction rule set Multiply the number by the rule's base value and format the result.
== in all rule sets Format the number unchanged
[] in normal rule Omit the optional text if the number is an even multiple of the rule's divisor
in negative-number rule Not allowed.
in improper-fraction rule Omit the optional text if the number is between 0 and 1 (same as specifying both an x.x rule and a 0.x rule)
in master rule Omit the optional text if the number is an integer (same as specifying both an x.x rule and an x.0 rule)
in proper-fraction rule Not allowed.
in rule in fraction rule set Omit the optional text if multiplying the number by the rule's base value yields 1.

The substitution descriptor (i.e., the text between the token characters) may take one of three forms:

a rule set name Perform the mathematical operation on the number, and format the result using the named rule set.
a DecimalFormat pattern Perform the mathematical operation on the number, and format the result using a DecimalFormat with the specified pattern.  The pattern must begin with 0 or #.
nothing Perform the mathematical operation on the number, and format the result using the rule set containing the current rule, except:
  • You can't have an empty substitution descriptor with a == substitution.
  • If you omit the substitution descriptor in a >> substitution in a fraction rule, format the result one digit at a time using the rule set containing the current rule.
  • If you omit the substitution descriptor in a << substitution in a rule in a fraction rule set, format the result using the default rule set for this formatter.

Whitespace is ignored between a rule set name and a rule set body, between a rule descriptor and a rule body, or between rules. If a rule body begins with an apostrophe, the apostrophe is ignored, but all text after it becomes significant (this is how you can have a rule's rule text begin with whitespace). There is no escape function: the semicolon is not allowed in rule set names or in rule text, and the colon is not allowed in rule set names. The characters beginning a substitution token are always treated as the beginning of a substitution token.

See the resource data and the demo program for annotated examples of real rule sets using these features.

User subclasses are not supported. While clients may write subclasses, such code will not necessarily work and will not be guaranteed to work stably from release to release.

Localizations

Constructors are available that allow the specification of localizations for the public rule sets (and also allow more control over what public rule sets are available). Localization data is represented as a textual description. The description represents an array of arrays of string. The first element is an array of the public rule set names, each of these must be one of the public rule set names that appear in the rules. Only names in this array will be treated as public rule set names by the API. Each subsequent element is an array of localizations of these names. The first element of one of these subarrays is the locale name, and the remaining elements are localizations of the public rule set names, in the same order as they were listed in the first arrray.

In the syntax, angle brackets '<', '>' are used to delimit the arrays, and comma ',' is used to separate elements of an array. Whitespace is ignored, unless quoted.

For example:

 < < foo, bar, baz >,
   < en, Foo, Bar, Baz >,
   < fr, 'le Foo', 'le Bar', 'le Baz' >
   < zh, \u7532, \u4e59, \u4e19 > >
 
Author:
Richard Gillam
See also:
NumberFormat

DecimalFormat ICU 2.0

Definition at line 503 of file rbnf.h.


Public Types

enum  EAlignmentFields {
  kIntegerField, kFractionField, kDecimalSeparatorField, kExponentSymbolField,
  kExponentSignField, kExponentField, kGroupingSeparatorField, kCurrencyField,
  kPercentField, kPermillField, kSignField, INTEGER_FIELD = kIntegerField,
  FRACTION_FIELD = kFractionField
}
enum  EStyles {
  kNumberStyle, kCurrencyStyle, kPercentStyle, kScientificStyle,
  kIsoCurrencyStyle, kPluralCurrencyStyle, kStyleCount
}

Public Member Functions

virtual Formatclone (void) const
virtual UnicodeStringformat (const DigitList &number, UnicodeString &appendTo, FieldPosition &pos, UErrorCode &status) const
virtual UnicodeStringformat (const DigitList &number, UnicodeString &appendTo, FieldPositionIterator *posIter, UErrorCode &status) const
virtual UnicodeStringformat (const StringPiece &number, UnicodeString &appendTo, FieldPositionIterator *posIter, UErrorCode &status) const
virtual UnicodeStringformat (int64_t number, UnicodeString &appendTo, FieldPositionIterator *posIter, UErrorCode &status) const
virtual UnicodeStringformat (int32_t number, UnicodeString &appendTo, FieldPositionIterator *posIter, UErrorCode &status) const
virtual UnicodeStringformat (double number, UnicodeString &appendTo, FieldPositionIterator *posIter, UErrorCode &status) const
UnicodeStringformat (int64_t number, UnicodeString &appendTo) const
virtual UnicodeStringformat (const Formattable &obj, UnicodeString &appendTo, FieldPositionIterator *posIter, UErrorCode &status) const
UnicodeStringformat (int32_t number, UnicodeString &output) const
UnicodeStringformat (double number, UnicodeString &output) const
UnicodeStringformat (const Formattable &obj, UnicodeString &result, UErrorCode &status) const
virtual UnicodeStringformat (const Formattable &obj, UnicodeString &toAppendTo, FieldPosition &pos, UErrorCode &status) const
virtual UnicodeStringformat (double number, const UnicodeString &ruleSetName, UnicodeString &toAppendTo, FieldPosition &pos, UErrorCode &status) const
virtual UnicodeStringformat (int64_t number, const UnicodeString &ruleSetName, UnicodeString &toAppendTo, FieldPosition &pos, UErrorCode &status) const
virtual UnicodeStringformat (int32_t number, const UnicodeString &ruleSetName, UnicodeString &toAppendTo, FieldPosition &pos, UErrorCode &status) const
virtual UnicodeStringformat (double number, UnicodeString &toAppendTo, FieldPosition &pos) const
virtual UnicodeStringformat (int64_t number, UnicodeString &toAppendTo, FieldPosition &pos) const
virtual UnicodeStringformat (int32_t number, UnicodeString &toAppendTo, FieldPosition &pos) const
const UChar * getCurrency () const
virtual UnicodeString getDefaultRuleSetName () const
virtual UClassID getDynamicClassID (void) const
Locale getLocale (ULocDataLocaleType type, UErrorCode &status) const
const char * getLocaleID (ULocDataLocaleType type, UErrorCode &status) const
int32_t getMaximumFractionDigits (void) const
int32_t getMaximumIntegerDigits (void) const
int32_t getMinimumFractionDigits (void) const
int32_t getMinimumIntegerDigits (void) const
virtual int32_t getNumberOfRuleSetDisplayNameLocales (void) const
virtual int32_t getNumberOfRuleSetNames () const
virtual UnicodeString getRules () const
virtual UnicodeString getRuleSetDisplayName (const UnicodeString &ruleSetName, const Locale &locale=Locale::getDefault())
virtual UnicodeString getRuleSetDisplayName (int32_t index, const Locale &locale=Locale::getDefault())
virtual Locale getRuleSetDisplayNameLocale (int32_t index, UErrorCode &status) const
virtual UnicodeString getRuleSetName (int32_t index) const
UBool isGroupingUsed (void) const
virtual UBool isLenient (void) const
UBool isParseIntegerOnly (void) const
UBool operator!= (const Format &other) const
RuleBasedNumberFormatoperator= (const RuleBasedNumberFormat &rhs)
virtual UBool operator== (const Format &other) const
virtual void parse (const UnicodeString &text, Formattable &result, UErrorCode &status) const
virtual void parse (const UnicodeString &text, Formattable &result, ParsePosition &parsePosition) const
virtual FormattableparseCurrency (const UnicodeString &text, Formattable &result, ParsePosition &pos) const
void parseObject (const UnicodeString &source, Formattable &result, UErrorCode &status) const
virtual void parseObject (const UnicodeString &source, Formattable &result, ParsePosition &parse_pos) const
 RuleBasedNumberFormat (const RuleBasedNumberFormat &rhs)
 RuleBasedNumberFormat (URBNFRuleSetTag tag, const Locale &locale, UErrorCode &status)
 RuleBasedNumberFormat (const UnicodeString &rules, const UnicodeString &localizations, const Locale &locale, UParseError &perror, UErrorCode &status)
 RuleBasedNumberFormat (const UnicodeString &rules, const Locale &locale, UParseError &perror, UErrorCode &status)
 RuleBasedNumberFormat (const UnicodeString &rules, const UnicodeString &localizations, UParseError &perror, UErrorCode &status)
 RuleBasedNumberFormat (const UnicodeString &rules, UParseError &perror, UErrorCode &status)
virtual void setCurrency (const UChar *theCurrency, UErrorCode &ec)
virtual void setDefaultRuleSet (const UnicodeString &ruleSetName, UErrorCode &status)
virtual void setGroupingUsed (UBool newValue)
virtual void setLenient (UBool enabled)
virtual void setMaximumFractionDigits (int32_t newValue)
virtual void setMaximumIntegerDigits (int32_t newValue)
virtual void setMinimumFractionDigits (int32_t newValue)
virtual void setMinimumIntegerDigits (int32_t newValue)
virtual void setParseIntegerOnly (UBool value)
virtual ~RuleBasedNumberFormat ()

Static Public Member Functions

static NumberFormat *U_EXPORT2 createCurrencyInstance (const Locale &inLocale, UErrorCode &)
static NumberFormat *U_EXPORT2 createCurrencyInstance (UErrorCode &)
static NumberFormat *U_EXPORT2 createInstance (const Locale &desiredLocale, EStyles choice, UErrorCode &success)
static NumberFormat *U_EXPORT2 createInstance (const Locale &inLocale, UErrorCode &)
static NumberFormat *U_EXPORT2 createInstance (UErrorCode &)
static NumberFormat *U_EXPORT2 createPercentInstance (const Locale &inLocale, UErrorCode &)
static NumberFormat *U_EXPORT2 createPercentInstance (UErrorCode &)
static NumberFormat *U_EXPORT2 createScientificInstance (const Locale &inLocale, UErrorCode &)
static NumberFormat *U_EXPORT2 createScientificInstance (UErrorCode &)
static StringEnumeration *U_EXPORT2 getAvailableLocales (void)
static const Locale *U_EXPORT2 getAvailableLocales (int32_t &count)
static UClassID U_EXPORT2 getStaticClassID (void)
static void U_EXPORT2 operator delete (void *, void *) U_NO_THROW
static void U_EXPORT2 operator delete (void *p) U_NO_THROW
static void U_EXPORT2 operator delete[] (void *p) U_NO_THROW
static void *U_EXPORT2 operator new (size_t, void *ptr) U_NO_THROW
static void *U_EXPORT2 operator new (size_t size) U_NO_THROW
static void *U_EXPORT2 operator new[] (size_t size) U_NO_THROW
static URegistryKey U_EXPORT2 registerFactory (NumberFormatFactory *toAdopt, UErrorCode &status)
static UBool U_EXPORT2 unregister (URegistryKey key, UErrorCode &status)

Protected Member Functions

virtual void getEffectiveCurrency (UChar *result, UErrorCode &ec) const
void setLocaleIDs (const char *valid, const char *actual)

Static Protected Member Functions

static void syntaxError (const UnicodeString &pattern, int32_t pos, UParseError &parseError)

Private Member Functions

void dispose ()
NFRuleSet * findRuleSet (const UnicodeString &name, UErrorCode &status) const
void format (double number, NFRuleSet &ruleSet)
CollatorgetCollator () const
DecimalFormatSymbolsgetDecimalFormatSymbols () const
NFRuleSet * getDefaultRuleSet () const
void init (const UnicodeString &rules, LocalizationInfo *localizations, UParseError &perror, UErrorCode &status)
void initDefaultRuleSet ()
 RuleBasedNumberFormat (const UnicodeString &description, LocalizationInfo *localizations, const Locale &locale, UParseError &perror, UErrorCode &status)
void stripWhitespace (UnicodeString &src)

Private Attributes

Collatorcollator
DecimalFormatSymbolsdecimalFormatSymbols
NFRuleSet * defaultRuleSet
UBool lenient
UnicodeStringlenientParseRules
Locale locale
LocalizationInfo * localizations
UBool noParse
NFRuleSet ** ruleSets

Friends

class FractionalPartSubstitution
class NFRule
class NFSubstitution

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