plurrule.h | Explore in Territory

// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
*******************************************************************************
* Copyright (C) 2008-2015, International Business Machines Corporation and
* others. All Rights Reserved.
*******************************************************************************
*
*
* File PLURRULE.H
*
* Modification History:*
*   Date        Name        Description
*
********************************************************************************
*/

#ifndef PLURRULE
#define PLURRULE

#include "unicode/utypes.h"

#if U_SHOW_CPLUSPLUS_API

/**
 * \file
 * \brief C++ API: PluralRules object
 */

#if !UCONFIG_NO_FORMATTING

#include "unicode/format.h"
#include "unicode/upluralrules.h"
#ifndef U_HIDE_INTERNAL_API
#include "unicode/numfmt.h"
#endif  /* U_HIDE_INTERNAL_API */

/**
 * Value returned by PluralRules::getUniqueKeywordValue() when there is no
 * unique value to return.
 * @stable ICU 4.8
 */
#define UPLRULES_NO_UNIQUE_VALUE …

U_NAMESPACE_BEGIN

class Hashtable;
class IFixedDecimal;
class FixedDecimal;
class RuleChain;
class PluralRuleParser;
class PluralKeywordEnumeration;
class AndConstraint;
class SharedPluralRules;
class StandardPluralRanges;

namespace number {
class FormattedNumber;
class FormattedNumberRange;
namespace impl {
class UFormattedNumberRangeData;
class DecimalQuantity;
class DecNum;
}
}

#ifndef U_HIDE_INTERNAL_API
DecimalQuantity;
#endif  /* U_HIDE_INTERNAL_API */

/**
 * 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 {@link #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:<pre>
 *   "one: n is 1; few: n in 2..4"</pre>
 *  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.
 *  </p><pre>
 *    "zero: n is 0; one: n is 1; zero: n mod 100 in 1..19"</pre>
 *  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...
 *  </p><pre>
 *    "one: n is 1; few: n mod 10 in 2..4 and n mod 100 not in 12..14"</pre>
 *  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...
 *  </p>
 *  <p>
 * Syntax:<pre>
 * \code
 * 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
 * \endcode
 * </pre></p>
 * <p>
 * <p>
 * The i, f, and v values are defined as follows:
 * </p>
 * <ul>
 * <li>i to be the integer digits.</li>
 * <li>f to be the visible fractional digits, as an integer.</li>
 * <li>v to be the number of visible fraction digits.</li>
 * <li>j is defined to only match integers. That is j is 3 fails if v != 0 (eg for 3.1 or 3.0).</li>
 * </ul>
 * <p>
 * Examples are in the following table:
 * </p>
 * <table border='1' style="border-collapse:collapse">
 * <tr>
 * <th>n</th>
 * <th>i</th>
 * <th>f</th>
 * <th>v</th>
 * </tr>
 * <tr>
 * <td>1.0</td>
 * <td>1</td>
 * <td align="right">0</td>
 * <td>1</td>
 * </tr>
 * <tr>
 * <td>1.00</td>
 * <td>1</td>
 * <td align="right">0</td>
 * <td>2</td>
 * </tr>
 * <tr>
 * <td>1.3</td>
 * <td>1</td>
 * <td align="right">3</td>
 * <td>1</td>
 * </tr>
 * <tr>
 * <td>1.03</td>
 * <td>1</td>
 * <td align="right">3</td>
 * <td>2</td>
 * </tr>
 * <tr>
 * <td>1.23</td>
 * <td>1</td>
 * <td align="right">23</td>
 * <td>2</td>
 * </tr>
 * </table>
 * <p>
 * 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).
 * </p>

 * An "identifier" is a sequence of characters that do not have the
 * Unicode Pattern_Syntax or Pattern_White_Space properties.
 * <p>
 * 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).
 *</p>
 * <p>
 * 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
 * {@link #select} method.
 * </p>
 *
 * Examples:<pre>
 * UnicodeString keyword = pl->select(number);
 * if (keyword== UnicodeString("one") {
 *     ...
 * }
 * else if ( ... )
 * </pre>
 * <strong>Note:</strong><br>
 *  <p>
 *   ICU defines plural rules for many locales based on CLDR <i>Language Plural Rules</i>.
 *   For these predefined rules, see CLDR page at
 *   https://unicode-org.github.io/cldr-staging/charts/latest/supplemental/language_plural_rules.html
 * </p>
 */
class U_I18N_API PluralRules : public UObject { … };

U_NAMESPACE_END

#endif /* #if !UCONFIG_NO_FORMATTING */

#endif /* U_SHOW_CPLUSPLUS_API */

#endif // _PLURRULE
//eof
chromium/third_party/icu/source/i18n/unicode/plurrule.h
