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Collator Class Reference

The Collator class performs locale-sensitive String comparison. More...

#include <coll.h>

Class diagram for Collator:

RuleBasedCollator

List of all members.


Public Members

enum  ECollationStrength { PRIMARY, SECONDARY, TERTIARY, IDENTICAL }
Base letter represents a primary difference. More...

enum  EComparisonResult { LESS, EQUAL, GREATER }
LESS is returned if source string is compared to be less than target string in the compare() method. More...

virtual ~Collator ()
Destructor. More...

virtual UBool operator== (const Collator& other) const
Returns true if "other" is the same as "this". More...

virtual UBool operator!= (const Collator& other) const
Returns true if "other" is not the same as "this". More...

virtual Collator* clone (void) const = 0
Makes a shallow copy of the current object. More...

virtual EComparisonResult compare ( const UnicodeString& source, const UnicodeString& target) const = 0
The comparison function compares the character data stored in two different strings. More...

virtual EComparisonResult compare ( const UnicodeString& source, const UnicodeString& target, int32_t length) const = 0
Does the same thing as compare but limits the comparison to a specified length

Example of use:. More...

virtual EComparisonResult compare ( const UChar* source, int32_t sourceLength, const UChar* target, int32_t targetLength) const = 0
The comparison function compares the character data stored in two different string arrays. More...

virtual CollationKeygetCollationKey (const UnicodeString& source, CollationKey& key, UErrorCode& status) const = 0
Transforms the string into a series of characters that can be compared with CollationKey::compareTo(). More...

virtual CollationKeygetCollationKey (const UChar *source, int32_t sourceLength, CollationKey& key, UErrorCode& status) const = 0
Transforms the string into a series of characters that can be compared with CollationKey::compareTo(). More...

virtual int32_t hashCode (void) const = 0
Generates the hash code for the collation object. More...

UBool greater ( const UnicodeString& source, const UnicodeString& target) const
Convenience method for comparing two strings based on the collation rules. More...

UBool greaterOrEqual ( const UnicodeString& source, const UnicodeString& target) const
Convenience method for comparing two strings based on the collation rules. More...

UBool equals ( const UnicodeString& source, const UnicodeString& target) const
Convenience method for comparing two strings based on the collation rules. More...

Normalizer::EMode getDecomposition (void) const
Get the decomposition mode of the collator object. More...

void setDecomposition (Normalizer::EMode mode)
Set the decomposition mode of the collator object. More...

ECollationStrength getStrength (void) const
Determines the minimum strength that will be use in comparison or transformation. More...

void setStrength ( ECollationStrength newStrength)
Sets the minimum strength to be used in comparison or transformation. More...

void getVersion (UVersionInfo info) const
Gets the version information for a Collator. More...

virtual UClassID getDynamicClassID (void) const = 0
Returns a unique class ID POLYMORPHICALLY. More...


Static Public Members

Collator* createInstance ( UErrorCode& err)
Creates the collator object for the current default locale. More...

Collator* createInstance ( const Locale& loc, UErrorCode& err)
Gets the table-based collation object for the desired locale. More...

UnicodeStringgetDisplayName ( const Locale& objectLocale, const Locale& displayLocale, UnicodeString& name)
Get name of the object for the desired Locale, in the desired langauge. More...

UnicodeStringgetDisplayName ( const Locale& objectLocale, UnicodeString& name)
Get name of the object for the desired Locale, in the langauge of the default locale. More...

const LocalegetAvailableLocales (int32_t& count)
Get the set of Locales for which Collations are installed. More...


Protected Members

 Collator ()
Constructors.

 Collator (ECollationStrength collationStrength, Normalizer::EMode decompositionMode)
 Collator (const Collator& other)
const Collator& operator= (const Collator& other)
Assignment operator.


Detailed Description

The Collator class performs locale-sensitive String comparison.

You use this class to build searching and sorting routines for natural language text.

Collator is an abstract base class. Subclasses implement specific collation strategies. One subclass, RuleBasedCollator, is currently provided and is applicable to a wide set of languages. Other subclasses may be created to handle more specialized needs.

Like other locale-sensitive classes, you can use the static factory method, getInstance, to obtain the appropriate Collator object for a given locale. You will only need to look at the subclasses of Collator if you need to understand the details of a particular collation strategy or if you need to modify that strategy.

The following example shows how to compare two strings using the Collator for the default locale.

 // Compare two strings in the default locale
 UErrorCode success = U_ZERO_ERROR;
 Collator* myCollator = Collator::createInstance(success);
 if( myCollator->compare("abc", "ABC") &lt; 0 ) {
     cout &lt;&lt; "abc is less than ABC" &lt;&lt; endl;
 }else{
     cout &lt;&lt; "abc is greater than or equal to ABC" &lt;&lt; endl;
 }
 

You can set a Collator's strength property to determine the level of difference considered significant in comparisons. Four strengths are provided: PRIMARY, SECONDARY, TERTIARY, and IDENTICAL. The exact assignment of strengths to language features is locale dependant. For example, in Czech, "e" and "f" are considered primary differences, while "e" and "\u00EA" are secondary differences, "e" and "E" are tertiary differences and "e" and "e" are identical. The following shows how both case and accents could be ignored for US English.

 //Get the Collator for US English and set its strength to PRIMARY
 UErrorCode success = U_ZERO_ERROR;
 Collator* usCollator = Collator::createInstance(Locale::US, success);
 usCollator->setStrength(Collator::PRIMARY);
 if( usCollator->compare("abc", "ABC") == 0 ) {
     cout &lt;&lt; "'abc' and 'ABC' strings are equivalent with strength PRIMARY" &lt;&lt; endl;
 }
 

For comparing Strings exactly once, the compare method provides the best performance. When sorting a list of Strings however, it is generally necessary to compare each String multiple times. In this case, CollationKeys provide better performance. The CollationKey class converts a String to a series of bits that can be compared bitwise against other CollationKeys. A CollationKey is created by a Collator object for a given String.

Note: Collators with different Locale, CollationStrength and DecompositionMode settings will return different sort orders for the same set of strings. Locales have specific collation rules, and the way in which secondary and tertiary differences are taken into account, for example, will result in a different sorting order for same strings.

See also:
RuleBasedCollator , CollationKey , CollationElementIterator , Locale , Normalizer
Version:
1.7 1/14/97
Author(s):
Helena Shih

Definition at line 140 of file coll.h.


Member Enumeration Documentation

enum Collator::ECollationStrength

Base letter represents a primary difference.

Set comparison level to PRIMARY to ignore secondary and tertiary differences. Use this to set the strength of a Collator object. Example of primary difference, "abc" < "abd"

Diacritical differences on the same base letter represent a secondary difference. Set comparison level to SECONDARY to ignore tertiary differences. Use this to set the strength of a Collator object. Example of secondary difference, "ä" >> "a".

Uppercase and lowercase versions of the same character represents a tertiary difference. Set comparison level to TERTIARY to include all comparison differences. Use this to set the strength of a Collator object. Example of tertiary difference, "abc" <<< "ABC".

Two characters are considered "identical" when they have the same unicode spellings. For example, "ä" == "ä".

ECollationStrength is also used to determine the strength of sort keys generated from Collator objects.

Enumeration values:
PRIMARY  
SECONDARY  
TERTIARY  
IDENTICAL  

Definition at line 166 of file coll.h.

enum Collator::EComparisonResult

LESS is returned if source string is compared to be less than target string in the compare() method.

EQUAL is returned if source string is compared to be equal to target string in the compare() method. GREATER is returned if source string is compared to be greater than target string in the compare() method.

See also:
Collator::compare()
Enumeration values:
LESS  
EQUAL  
GREATER  

Definition at line 182 of file coll.h.


Member Function Documentation

virtual Collator::~Collator () [virtual]

Destructor.

Stable:

UBool Collator::operator== (const Collator & other) const [inline, virtual]

Returns true if "other" is the same as "this".

Stable:

Reimplemented in RuleBasedCollator.

Definition at line 576 of file coll.h.

UBool Collator::operator!= (const Collator & other) const [inline, virtual]

Returns true if "other" is not the same as "this".

Stable:

Reimplemented in RuleBasedCollator.

Definition at line 585 of file coll.h.

virtual Collator * Collator::clone (void) const [pure virtual]

Makes a shallow copy of the current object.

Stable:

Reimplemented in RuleBasedCollator.

virtual EComparisonResult Collator::compare (const UnicodeString & source, const UnicodeString & target) const [pure virtual]

The comparison function compares the character data stored in two different strings.

Returns information about whether a string is less than, greater than or equal to another string.

Example of use:

 .       UErrorCode status = U_ZERO_ERROR;
 .       Collator *myCollation = Collator::createInstance(Locale::US, status);
 .       if (U_FAILURE(status)) return;
 .       myCollation->setStrength(Collator::PRIMARY);
 .       // result would be Collator::EQUAL ("abc" == "ABC")
 .       // (no primary difference between "abc" and "ABC")
 .       Collator::EComparisonResult result = myCollation->compare("abc", "ABC");
 .       myCollation->setStrength(Collator::TERTIARY);
 .       // result would be Collator::LESS (abc" &lt;&lt;&lt; "ABC")
 .       // (with tertiary difference between "abc" and "ABC")
 .       Collator::EComparisonResult result = myCollation->compare("abc", "ABC");
 
Parameters:
source   the source string to be compared with.
target   the string that is to be compared with the source string.
Returns:
Returns a byte value. GREATER if source is greater than target; EQUAL if source is equal to target; LESS if source is less than target
Stable:

Reimplemented in RuleBasedCollator.

virtual EComparisonResult Collator::compare (const UnicodeString & source, const UnicodeString & target, int32_t length) const [pure virtual]

Does the same thing as compare but limits the comparison to a specified length

Example of use:.

 .       UErrorCode status = U_ZERO_ERROR;
 .       Collator *myCollation = Collator::createInstance(Locale::US, status);
 .       if (U_FAILURE(status)) return;
 .       myCollation->setStrength(Collator::PRIMARY);
 .       // result would be Collator::EQUAL ("abc" == "ABC")
 .       // (no primary difference between "abc" and "ABC")
 .       Collator::EComparisonResult result = myCollation->compare("abc", "ABC",3);
 .       myCollation->setStrength(Collator::TERTIARY);
 .       // result would be Collator::LESS (abc" &lt;&lt;&lt; "ABC")
 .       // (with tertiary difference between "abc" and "ABC")
 .       Collator::EComparisonResult result = myCollation->compare("abc", "ABC",3);
 
Parameters:
source   the source string to be compared with.
target   the string that is to be compared with the source string.
length   the length the comparison is limitted to
Returns:
Returns a byte value. GREATER if source (up to the specified length) is greater than target; EQUAL if source (up to specified length) is equal to target; LESS if source (up to the specified length) is less than target.
Draft:

Reimplemented in RuleBasedCollator.

virtual EComparisonResult Collator::compare (const UChar * source, int32_t sourceLength, const UChar * target, int32_t targetLength) const [pure virtual]

The comparison function compares the character data stored in two different string arrays.

Returns information about whether a string array is less than, greater than or equal to another string array.

Example of use:

 .       UErrorCode status = U_ZERO_ERROR;
 .       Collator *myCollation = Collator::createInstance(Locale::US, status);
 .       if (U_FAILURE(status)) return;
 .       myCollation->setStrength(Collator::PRIMARY);
 .       // result would be Collator::EQUAL ("abc" == "ABC")
 .       // (no primary difference between "abc" and "ABC")
 .       Collator::EComparisonResult result = myCollation->compare(L"abc", 3, L"ABC", 3);
 .       myCollation->setStrength(Collator::TERTIARY);
 .       // result would be Collator::LESS (abc" &lt;&lt;&lt; "ABC")
 .       // (with tertiary difference between "abc" and "ABC")
 .       Collator::EComparisonResult result = myCollation->compare(L"abc", 3, L"ABC", 3);
 
Parameters:
source   the source string array to be compared with.
sourceLength   the length of the source string array. If this value is equal to -1, the string array is null-terminated.
target   the string that is to be compared with the source string.
targetLength   the length of the target string array. If this value is equal to -1, the string array is null-terminated.
Returns:
Returns a byte value. GREATER if source is greater than target; EQUAL if source is equal to target; LESS if source is less than target
Stable:

Reimplemented in RuleBasedCollator.

virtual CollationKey & Collator::getCollationKey (const UnicodeString & source, CollationKey & key, UErrorCode & status) const [pure virtual]

Transforms the string into a series of characters that can be compared with CollationKey::compareTo().

It is not possible to restore the original string from the chars in the sort key. The generated sort key handles only a limited number of ignorable characters.

Use CollationKey::equals or CollationKey::compare to compare the generated sort keys.

Example of use:

 .       UErrorCode status = U_ZERO_ERROR;
 .       Collator *myCollation = Collator::createInstance(Locale::US, status);
 .       if (U_FAILURE(status)) return;
 .       myCollation->setStrength(Collator::PRIMARY);
 .       UErrorCode key1Status, key2Status;
 .       CollationKey CollationKey1
 .       CollationKey1 = myCollation->getCollationKey("abc", CollationKey1, key1Status);
 .       CollationKey CollationKey2
 .       CollationKey2 = myCollation->getCollationKey("ABC", CollationKey2, key2Status);
 .       if (U_FAILURE(key1Status) || U_FAILURE(key2Status)) { delete myCollation; return; }
 .       // Use CollationKey::compare() to compare the sort keys
 .       // result would be 0 (CollationKey1 == CollationKey2)
 .       int result = CollationKey1.compare(CollationKey2);
 .       myCollation->setStrength(Collator::TERTIARY);
 .       CollationKey1 = myCollation->getCollationKey("abc", CollationKey1, key1Status);
 .       CollationKey2 = myCollation->getCollationKey("ABC", CollationKey2, key2Status);
 .       if (U_FAILURE(key1Status) || U_FAILURE(key2Status)) { delete myCollation; return; }
 .       // Use CollationKey::compareTo to compare the collation keys
 .       // result would be -1 (CollationKey1 &lt; CollationKey2)
 .       result = CollationKey1.compareTo(CollationKey2);
 .       delete myCollation;
 

If the source string is null, a null collation key will be returned.

Parameters:
source   the source string to be transformed into a sort key.
key   the collation key to be filled in
Returns:
the collation key of the string based on the collation rules.
See also:
CollationKey::compare
Draft:

Reimplemented in RuleBasedCollator.

virtual CollationKey & Collator::getCollationKey (const UChar * source, int32_t sourceLength, CollationKey & key, UErrorCode & status) const [pure virtual]

Transforms the string into a series of characters that can be compared with CollationKey::compareTo().

It is not possible to restore the original string from the chars in the sort key. The generated sort key handles only a limited number of ignorable characters.

Use CollationKey::equals or CollationKey::compare to compare the generated sort keys.

If the source string is null, a null collation key will be returned.

Parameters:
source   the source string to be transformed into a sort key.
sourceLength   length of the collation key
key   the collation key to be filled in
Returns:
the collation key of the string based on the collation rules.
See also:
CollationKey::compare
Draft:

Reimplemented in RuleBasedCollator.

virtual int32_t Collator::hashCode (void) const [pure virtual]

Generates the hash code for the collation object.

Stable:

Reimplemented in RuleBasedCollator.

UBool Collator::greater (const UnicodeString & source, const UnicodeString & target) const

Convenience method for comparing two strings based on the collation rules.

Parameters:
source   the source string to be compared with.
target   the target string to be compared with.
Returns:
true if the first string is greater than the second one, according to the collation rules. false, otherwise.
See also:
Collator::compare()
Stable:

UBool Collator::greaterOrEqual (const UnicodeString & source, const UnicodeString & target) const

Convenience method for comparing two strings based on the collation rules.

Parameters:
source   the source string to be compared with.
target   the target string to be compared with.
Returns:
true if the first string is greater than or equal to the second one, according to the collation rules. false, otherwise.
See also:
Collator::compare()
Stable:

UBool Collator::equals (const UnicodeString & source, const UnicodeString & target) const

Convenience method for comparing two strings based on the collation rules.

Parameters:
source   the source string to be compared with.
target   the target string to be compared with.
Returns:
true if the strings are equal according to the collation rules. false, otherwise.
See also:
Collator::compare()
Stable:

Normalizer::EMode Collator::getDecomposition (void) const [inline]

Get the decomposition mode of the collator object.

Returns:
the decomposition mode
See also:
Collator::setDecomposition()
Stable:

Definition at line 599 of file coll.h.

void Collator::setDecomposition (Normalizer::EMode mode)

Set the decomposition mode of the collator object.

success is equal to U_ILLEGAL_ARGUMENT_ERROR if error occurs.

Parameters:
the   new decomposition mode
See also:
Collator::getDecomposition()
Stable:

Collator::ECollationStrength Collator::getStrength (void) const [inline]

Determines the minimum strength that will be use in comparison or transformation.

E.g. with strength == SECONDARY, the tertiary difference is ignored

E.g. with strength == PRIMARY, the secondary and tertiary difference are ignored.

Returns:
the current comparison level.
See also:
Collator::setStrength()
Stable:

Definition at line 593 of file coll.h.

void Collator::setStrength (ECollationStrength newStrength)

Sets the minimum strength to be used in comparison or transformation.

Example of use:

 .       UErrorCode status = U_ZERO_ERROR;
 .       Collator *myCollation = Collator::createInstance(Locale::US, status);
 .       if (U_FAILURE(status)) return;
 .       myCollation->setStrength(Collator::PRIMARY);
 .       // result will be "abc" == "ABC"
 .       // tertiary differences will be ignored
 .       Collator::ComparisonResult result = myCollation->compare("abc", "ABC");
 
See also:
Collator::getStrength()
Parameters:
newStrength   the new comparison level.
Stable:

void Collator::getVersion (UVersionInfo info) const

Gets the version information for a Collator.

Parameters:
info   the version # information, the result will be filled in
Stable:

virtual UClassID Collator::getDynamicClassID (void) const [pure virtual]

Returns a unique class ID POLYMORPHICALLY.

Pure virtual method. 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.

Concrete subclasses of Format must implement getDynamicClassID() and also a static method and data member:

static UClassID getStaticClassID() { return (UClassID)&fgClassID; } static char fgClassID;

Returns:
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:

Reimplemented in RuleBasedCollator.

Collator * Collator::createInstance (UErrorCode & err) [static]

Creates the collator object for the current default locale.

The default locale is determined by Locale::getDefault().

Returns:
the collation object of the default locale.(for example, en_US)
See also:
Locale::getDefault() The UErrorCode& err parameter is used to return status information to the user. To check whether the construction succeeded or not, you should check the value of U_SUCCESS(err). If you wish more detailed information, you can check for informational error results which still indicate success. U_USING_FALLBACK_ERROR indicates that a fall back locale was used. For example, 'de_CH' was requested, but nothing was found there, so 'de' was used. U_USING_DEFAULT_ERROR indicates that the default locale data was used; neither the requested locale nor any of its fall back locales could be found. The caller owns the returned object and is responsible for deleting it.
Stable:

Collator * Collator::createInstance (const Locale & loc, UErrorCode & err) [static]

Gets the table-based collation object for the desired locale.

The resource of the desired locale will be loaded by ResourceLoader. Locale::ENGLISH is the base collation table and all other languages are built on top of it with additional language-specific modifications.

Parameters:
desiredLocale   the desired locale to create the collation table with.
Returns:
the created table-based collation object based on the desired locale.
See also:
Locale , ResourceLoader The UErrorCode& err parameter is used to return status information to the user. To check whether the construction succeeded or not, you should check the value of U_SUCCESS(err). If you wish more detailed information, you can check for informational error results which still indicate success. U_USING_FALLBACK_ERROR indicates that a fall back locale was used. For example, 'de_CH' was requested, but nothing was found there, so 'de' was used. U_USING_DEFAULT_ERROR indicates that the default locale data was used; neither the requested locale nor any of its fall back locales could be found. The caller owns the returned object and is responsible for deleting it.
Stable:

UnicodeString & Collator::getDisplayName (const Locale & objectLocale, const Locale & displayLocale, UnicodeString & name) [static]

Get name of the object for the desired Locale, in the desired langauge.

Parameters:
objectLocale   must be from getAvailableLocales
displayLocale   specifies the desired locale for output
name   the fill-in parameter of the return value
Returns:
display-able name of the object for the object locale in the desired language
Stable:

UnicodeString & Collator::getDisplayName (const Locale & objectLocale, UnicodeString & name) [static]

Get name of the object for the desired Locale, in the langauge of the default locale.

Parameters:
objectLocale   must be from getAvailableLocales
name   the fill-in parameter of the return value
Returns:
name of the object for the desired locale in the default language
Stable:

const Locale * Collator::getAvailableLocales (int32_t & count) [static]

Get the set of Locales for which Collations are installed.

Parameters:
count   the output parameter of number of elements in the locale list
Returns:
the list of available locales which collations are installed
Stable:

Collator::Collator () [protected]

Constructors.

Collator::Collator (ECollationStrength collationStrength, Normalizer::EMode decompositionMode) [protected]

Collator::Collator (const Collator & other) [protected]

const Collator & Collator::operator= (const Collator & other) [protected]

Assignment operator.


The documentation for this class was generated from the following file:
Generated at Wed Aug 16 16:05:42 2000 for ICU1.6 by doxygen 1.0.0 written by Dimitri van Heesch, © 1997-1999