Defines rules for mapping non-negative numeric values onto a small set of keywords. More...

#include <plurrule.h>

Inheritance diagram for icu::PluralRules:

Public Member Functions
	PluralRules (UErrorCode &status)
	Constructor. More...

	PluralRules (const PluralRules &other)
	Copy constructor. More...

virtual	~PluralRules ()
	Destructor. More...

PluralRules *	clone () const
	Clone. More...

PluralRules &	operator= (const PluralRules &)
	Assignment operator. More...

UnicodeString	select (int32_t number) const
	Given an integer, returns the keyword of the first rule that applies to the number. More...

UnicodeString	select (double number) const
	Given a floating-point number, returns the keyword of the first rule that applies to the number. More...

UnicodeString	select (const number::FormattedNumber &number, UErrorCode &status) const
	Given a formatted number, returns the keyword of the first rule that applies to the number. More...

UnicodeString	select (const number::FormattedNumberRange &range, UErrorCode &status) const
	Given a formatted number range, returns the overall plural form of the range. More...

UnicodeString	select (const IFixedDecimal &number) const

UnicodeString	select (const number::impl::UFormattedNumberRangeData *urange, UErrorCode &status) const

StringEnumeration *	getKeywords (UErrorCode &status) const
	Returns a list of all rule keywords used in this `PluralRules` object. More...

double	getUniqueKeywordValue (const UnicodeString &keyword)
	Deprecated Function, does not return useful results. More...

int32_t	getAllKeywordValues (const UnicodeString &keyword, double *dest, int32_t destCapacity, UErrorCode &status)
	Deprecated Function, does not produce useful results. More...

int32_t	getSamples (const UnicodeString &keyword, double *dest, int32_t destCapacity, UErrorCode &status)
	Returns sample values for which select() would return the keyword. More...

int32_t	getSamples (const UnicodeString &keyword, DecimalQuantity *dest, int32_t destCapacity, UErrorCode &status)
	Internal-only function that returns DecimalQuantitys instead of doubles. More...

UBool	isKeyword (const UnicodeString &keyword) const
	Returns true if the given keyword is defined in this `PluralRules` object. More...

UnicodeString	getKeywordOther () const
	Returns keyword for default plural form. More...

UnicodeString	getRules () const

virtual bool	operator== (const PluralRules &other) const
	Compares the equality of two PluralRules objects. More...

bool	operator!= (const PluralRules &other) const
	Compares the inequality of two PluralRules objects. More...

virtual UClassID	getDynamicClassID () const override
	ICU "poor man's RTTI", returns a UClassID for the actual class. More...

Public Member Functions inherited from icu::UObject
virtual	~UObject ()
	Destructor. More...

virtual UClassID	getDynamicClassID () const
	ICU4C "poor man's RTTI", returns a UClassID for the actual ICU class. More...

Static Public Member Functions
static PluralRules *	createRules (const UnicodeString &description, UErrorCode &status)
	Creates a PluralRules from a description if it is parsable, otherwise returns NULL. More...

static PluralRules *	createDefaultRules (UErrorCode &status)
	The default rules that accept any number. More...

static PluralRules *	forLocale (const Locale &locale, UErrorCode &status)
	Provides access to the predefined cardinal-number `PluralRules` for a given locale. More...

static PluralRules *	forLocale (const Locale &locale, UPluralType type, UErrorCode &status)
	Provides access to the predefined `PluralRules` for a given locale and the plural type. More...

static StringEnumeration *	getAvailableLocales (UErrorCode &status)
	Return a StringEnumeration over the locales for which there is plurals data. More...

static PluralRules *	internalForLocale (const Locale &locale, UPluralType type, UErrorCode &status)
	For ICU use only. More...

static const SharedPluralRules *	createSharedInstance (const Locale &locale, UPluralType type, UErrorCode &status)
	For ICU use only. More...

static UClassID	getStaticClassID (void)
	ICU "poor man's RTTI", returns a UClassID for this class. More...

Friends
class	PluralRuleParser

Detailed Description

Defines rules for mapping non-negative numeric values onto a small set of keywords.

Rules are constructed from a text description, consisting of a series of keywords and conditions. The select method examines each condition in order and returns the keyword for the first condition that matches the number. If none match, default rule(other) is returned.

For more information, details, and tips for writing rules, see the LDML spec, Part 3.5 Language Plural Rules: https://www.unicode.org/reports/tr35/tr35-numbers.html#Language_Plural_Rules

Examples:

   "one: n is 1; few: n in 2..4"

This defines two rules, for 'one' and 'few'. The condition for 'one' is "n is 1" which means that the number must be equal to 1 for this condition to pass. The condition for 'few' is "n in 2..4" which means that the number must be between 2 and 4 inclusive for this condition to pass. All other numbers are assigned the keyword "other" by the default rule.

    "zero: n is 0; one: n is 1; zero: n mod 100 in 1..19"

This illustrates that the same keyword can be defined multiple times. Each rule is examined in order, and the first keyword whose condition passes is the one returned. Also notes that a modulus is applied to n in the last rule. Thus its condition holds for 119, 219, 319...

    "one: n is 1; few: n mod 10 in 2..4 and n mod 100 not in 12..14"

This illustrates conjunction and negation. The condition for 'few' has two parts, both of which must be met: "n mod 10 in 2..4" and "n mod 100 not in 12..14". The first part applies a modulus to n before the test as in the previous example. The second part applies a different modulus and also uses negation, thus it matches all numbers not in 12, 13, 14, 112, 113, 114, 212, 213, 214...

Syntax:

 rules         = rule (';' rule)*
rule          = keyword ':' condition
keyword       = <identifier>
condition     = and_condition ('or' and_condition)*
and_condition = relation ('and' relation)*
relation      = is_relation | in_relation | within_relation | 'n' <EOL>
is_relation   = expr 'is' ('not')? value
in_relation   = expr ('not')? 'in' range_list
within_relation = expr ('not')? 'within' range
expr          = ('n' | 'i' | 'f' | 'v' | 'j') ('mod' value)?
range_list    = (range | value) (',' range_list)*
value         = digit+  ('.' digit+)?
digit         = 0|1|2|3|4|5|6|7|8|9
range         = value'..'value

</p

‍

The i, f, and v values are defined as follows:

i to be the integer digits.

f to be the visible fractional digits, as an integer.

v to be the number of visible fraction digits.

j is defined to only match integers. That is j is 3 fails if v != 0 (eg for 3.1 or 3.0).

Examples are in the following table:

n i f v

1.0 1 0 1

1.00 1 0 2

1.3 1 3 1

1.03 1 3 2

1.23 1 23 2

The difference between 'in' and 'within' is that 'in' only includes integers in the specified range, while 'within' includes all values. Using 'within' with a range_list consisting entirely of values is the same as using 'in' (it's not an error).

An "identifier" is a sequence of characters that do not have the Unicode Pattern_Syntax or Pattern_White_Space properties.

The difference between 'in' and 'within' is that 'in' only includes integers in the specified range, while 'within' includes all values. Using 'within' with a range_list consisting entirely of values is the same as using 'in' (it's not an error).

Keywords could be defined by users or from ICU locale data. There are 6 predefined values in ICU - 'zero', 'one', 'two', 'few', 'many' and 'other'. Callers need to check the value of keyword returned by select method.

Examples:

 UnicodeString keyword = pl->select(number);
 if (keyword== UnicodeString("one") {
     ...
 }
 else if ( ... )

Note:

ICU defines plural rules for many locales based on CLDR Language Plural Rules. For these predefined rules, see CLDR page at https://unicode-org.github.io/cldr-staging/charts/latest/supplemental/language_plural_rules.html

Definition at line 212 of file plurrule.h.

Constructor & Destructor Documentation

◆ PluralRules() [1/2]

icu::PluralRules::PluralRules ( UErrorCode & status )

Constructor.

Parameters

status Output param set to success/failure code on exit, which must not indicate a failure before the function call.

Stable:: ICU 4.0

◆ PluralRules() [2/2]

icu::PluralRules::PluralRules ( const PluralRules & other )

Copy constructor.

Stable:: ICU 4.0

◆ ~PluralRules()

virtual icu::PluralRules::~PluralRules ( )

virtual

Destructor.

Stable:: ICU 4.0

Member Function Documentation

◆ clone()

PluralRules * icu::PluralRules::clone ( ) const

Clone.

Stable:: ICU 4.0

◆ createDefaultRules()

static PluralRules * icu::PluralRules::createDefaultRules ( UErrorCode & status )

static

The default rules that accept any number.

Parameters

status Output param set to success/failure code on exit, which must not indicate a failure before the function call.

Returns: new PluralRules pointer. NULL if there is an error.

Stable:: ICU 4.0

◆ createRules()

static PluralRules * icu::PluralRules::createRules	(	const UnicodeString &	description,
		UErrorCode &	status
	)

static

Creates a PluralRules from a description if it is parsable, otherwise returns NULL.

Parameters

description	rule description
status	Output param set to success/failure code on exit, which must not indicate a failure before the function call.

Returns: new PluralRules pointer. NULL if there is an error.

Stable:: ICU 4.0

◆ createSharedInstance()

static const SharedPluralRules * icu::PluralRules::createSharedInstance	(	const Locale &	locale,
		UPluralType	type,
		UErrorCode &	status
	)

static

For ICU use only.

Returns handle to the shared, cached PluralRules instance. Caller must call removeRef() on returned value once it is done with the shared instance.

Internal:: Do not use. This API is for internal use only.

◆ forLocale() [1/2]

static PluralRules * icu::PluralRules::forLocale	(	const Locale &	locale,
		UErrorCode &	status
	)

static

Provides access to the predefined cardinal-number PluralRules for a given locale.

Same as forLocale(locale, UPLURAL_TYPE_CARDINAL, status).

Parameters

locale	The locale for which a `PluralRules` object is returned.
status	Output param set to success/failure code on exit, which must not indicate a failure before the function call.

Returns: The predefined PluralRules object pointer for this locale. If there's no predefined rules for this locale, the rules for the closest parent in the locale hierarchy that has one will be returned. The final fallback always returns the default 'other' rules.

Stable:: ICU 4.0

◆ forLocale() [2/2]

static PluralRules * icu::PluralRules::forLocale	(	const Locale &	locale,
		UPluralType	type,
		UErrorCode &	status
	)

static

Provides access to the predefined PluralRules for a given locale and the plural type.

Parameters

locale	The locale for which a `PluralRules` object is returned.
type	The plural type (e.g., cardinal or ordinal).
status	Output param set to success/failure code on exit, which must not indicate a failure before the function call.

Returns: The predefined PluralRules object pointer for this locale. If there's no predefined rules for this locale, the rules for the closest parent in the locale hierarchy that has one will be returned. The final fallback always returns the default 'other' rules.

Stable:: ICU 50

◆ getAllKeywordValues()

int32_t icu::PluralRules::getAllKeywordValues	(	const UnicodeString &	keyword,
		double *	dest,
		int32_t	destCapacity,
		UErrorCode &	status
	)

Deprecated Function, does not produce useful results.

Originally intended to return all the values for which select() would return the keyword. If the keyword is unknown, returns no values, but this is not an error. If the number of values is unlimited, returns no values and -1 as the count.

The number of returned values is typically small.

Parameters

keyword	The keyword.
dest	Array into which to put the returned values. May be NULL if destCapacity is 0.
destCapacity	The capacity of the array, must be at least 0.
status	The error code. Deprecated function, always sets U_UNSUPPORTED_ERROR.

Returns: The count of values available, or -1. This count can be larger than destCapacity, but no more than destCapacity values will be written.

Deprecated:: ICU 55

◆ getAvailableLocales()

static StringEnumeration * icu::PluralRules::getAvailableLocales ( UErrorCode & status )

static

Return a StringEnumeration over the locales for which there is plurals data.

Returns: a StringEnumeration over the locales available.

Internal:: Do not use. This API is for internal use only.

◆ getDynamicClassID()

virtual UClassID icu::PluralRules::getDynamicClassID ( ) const

overridevirtual

ICU "poor man's RTTI", returns a UClassID for the actual class.

Stable:: ICU 4.0

Reimplemented from icu::UObject.

◆ getKeywordOther()

UnicodeString icu::PluralRules::getKeywordOther ( ) const

Returns keyword for default plural form.

Returns: keyword for default plural form.

Stable:: ICU 4.0

◆ getKeywords()

StringEnumeration * icu::PluralRules::getKeywords ( UErrorCode & status ) const

Returns a list of all rule keywords used in this PluralRules object.

The rule 'other' is always present by default.

Parameters

status Output param set to success/failure code on exit, which must not indicate a failure before the function call.

Returns: StringEnumeration with the keywords. The caller must delete the object.

Stable:: ICU 4.0

◆ getRules()

UnicodeString icu::PluralRules::getRules ( ) const

Internal:: Do not use. This API is for internal use only.

◆ getSamples() [1/2]

int32_t icu::PluralRules::getSamples	(	const UnicodeString &	keyword,
		DecimalQuantity *	dest,
		int32_t	destCapacity,
		UErrorCode &	status
	)

Internal-only function that returns DecimalQuantitys instead of doubles.

Returns sample values for which select() would return the keyword. If the keyword is unknown, returns no values, but this is not an error.

The number of returned values is typically small.

Parameters

keyword	The keyword.
dest	Array into which to put the returned values. May be NULL if destCapacity is 0.
destCapacity	The capacity of the array, must be at least 0.
status	The error code.

Returns: The count of values written. If more than destCapacity samples are available, then only destCapacity are written, and destCapacity is returned as the count, rather than setting a U_BUFFER_OVERFLOW_ERROR. (The actual number of keyword values could be unlimited.)

Internal:: Do not use. This API is for internal use only.

◆ getSamples() [2/2]

int32_t icu::PluralRules::getSamples	(	const UnicodeString &	keyword,
		double *	dest,
		int32_t	destCapacity,
		UErrorCode &	status
	)

Returns sample values for which select() would return the keyword.

If the keyword is unknown, returns no values, but this is not an error.

The number of returned values is typically small.

Parameters

keyword	The keyword.
dest	Array into which to put the returned values. May be NULL if destCapacity is 0.
destCapacity	The capacity of the array, must be at least 0.
status	The error code.

Returns: The count of values written. If more than destCapacity samples are available, then only destCapacity are written, and destCapacity is returned as the count, rather than setting a U_BUFFER_OVERFLOW_ERROR. (The actual number of keyword values could be unlimited.)

Stable:: ICU 4.8

◆ getStaticClassID()

static UClassID icu::PluralRules::getStaticClassID ( void )

static

ICU "poor man's RTTI", returns a UClassID for this class.

Stable:: ICU 4.0

◆ getUniqueKeywordValue()

double icu::PluralRules::getUniqueKeywordValue ( const UnicodeString & keyword )

Deprecated Function, does not return useful results.

Originally intended to return a unique value for this keyword if it exists, else the constant UPLRULES_NO_UNIQUE_VALUE.

Parameters

keyword The keyword.

Returns: Stub deprecated function returns UPLRULES_NO_UNIQUE_VALUE always.

Deprecated:: ICU 55

◆ internalForLocale()

static PluralRules * icu::PluralRules::internalForLocale	(	const Locale &	locale,
		UPluralType	type,
		UErrorCode &	status
	)

static

For ICU use only.

creates a SharedPluralRules object

Internal:: Do not use. This API is for internal use only.

◆ isKeyword()

UBool icu::PluralRules::isKeyword ( const UnicodeString & keyword ) const

Returns true if the given keyword is defined in this PluralRules object.

Parameters

keyword the input keyword.

Returns: true if the input keyword is defined. Otherwise, return false.

Stable:: ICU 4.0

◆ operator!=()

bool icu::PluralRules::operator!= ( const PluralRules & other ) const

inline

Compares the inequality of two PluralRules objects.

Parameters

other The PluralRules object to be compared with.

Returns: true if the given PluralRules is not the same as this PluralRules; false otherwise.

Stable:: ICU 4.0

Definition at line 547 of file plurrule.h.

References icu::operator==().

◆ operator=()

PluralRules & icu::PluralRules::operator= ( const PluralRules & )

Assignment operator.

Stable:: ICU 4.0

◆ operator==()

virtual bool icu::PluralRules::operator== ( const PluralRules & other ) const

virtual

Compares the equality of two PluralRules objects.

Parameters

other The other PluralRules object to be compared with.

Returns: true if the given PluralRules is the same as this PluralRules; false otherwise.

Stable:: ICU 4.0

◆ select() [1/6]

UnicodeString icu::PluralRules::select ( const IFixedDecimal & number ) const

Internal:: Do not use. This API is for internal use only.

◆ select() [2/6]

UnicodeString icu::PluralRules::select	(	const number::FormattedNumber &	number,
		UErrorCode &	status
	)		const

Given a formatted number, returns the keyword of the first rule that applies to the number.

This function can be used with isKeyword* functions to determine the keyword for default plural rules.

A FormattedNumber allows you to specify an exponent or trailing zeros, which can affect the plural category. To get a FormattedNumber, see NumberFormatter.

Parameters

number	The number for which the rule has to be determined.
status	Set if an error occurs while selecting plural keyword. This could happen if the FormattedNumber is invalid.

Returns: The keyword of the selected rule.

Stable:: ICU 64

◆ select() [3/6]

UnicodeString icu::PluralRules::select	(	const number::FormattedNumberRange &	range,
		UErrorCode &	status
	)		const

Given a formatted number range, returns the overall plural form of the range.

For example, "3-5" returns "other" in English.

To get a FormattedNumberRange, see NumberRangeFormatter.

This method only works if PluralRules was created with a locale. If it was created from PluralRules::createRules(), this method sets status code U_UNSUPPORTED_ERROR.

Parameters

range	The number range onto which the rules will be applied.
status	Set if an error occurs while selecting plural keyword. This could happen if the FormattedNumberRange is invalid, or if plural ranges data is unavailable.

Returns: The keyword of the selected rule.

Stable:: ICU 68

◆ select() [4/6]

UnicodeString icu::PluralRules::select	(	const number::impl::UFormattedNumberRangeData *	urange,
		UErrorCode &	status
	)		const

Internal:: Do not use. This API is for internal use only.

◆ select() [5/6]

UnicodeString icu::PluralRules::select ( double number ) const

Given a floating-point number, returns the keyword of the first rule that applies to the number.

This function can be used with isKeyword* functions to determine the keyword for default plural rules.

Parameters

number The number for which the rule has to be determined.

Returns: The keyword of the selected rule.

Stable:: ICU 4.0

◆ select() [6/6]

UnicodeString icu::PluralRules::select ( int32_t number ) const

Given an integer, returns the keyword of the first rule that applies to the number.

This function can be used with isKeyword* functions to determine the keyword for default plural rules.

Parameters

number The number for which the rule has to be determined.

Returns: The keyword of the selected rule.

Stable:: ICU 4.0

Friends And Related Function Documentation

◆ PluralRuleParser

friend class PluralRuleParser

friend

Definition at line 581 of file plurrule.h.

The documentation for this class was generated from the following file:

plurrule.h

Public Member Functions

Static Public Member Functions

Friends

Detailed Description

Constructor & Destructor Documentation

◆ PluralRules() [1/2]

◆ PluralRules() [2/2]

◆ ~PluralRules()

Member Function Documentation

◆ clone()

◆ createDefaultRules()

◆ createRules()

◆ createSharedInstance()

◆ forLocale() [1/2]

◆ forLocale() [2/2]

◆ getAllKeywordValues()

◆ getAvailableLocales()

◆ getDynamicClassID()

◆ getKeywordOther()

◆ getKeywords()

◆ getRules()

◆ getSamples() [1/2]

◆ getSamples() [2/2]

◆ getStaticClassID()

◆ getUniqueKeywordValue()

◆ internalForLocale()

◆ isKeyword()

◆ operator!=()

◆ operator=()

◆ operator==()

◆ select() [1/6]

◆ select() [2/6]

◆ select() [3/6]

◆ select() [4/6]

◆ select() [5/6]

◆ select() [6/6]

Friends And Related Function Documentation

◆ PluralRuleParser