Xapian::Stem Class Reference

Class representing a stemming algorithm. More...

#include <stem.h>

Public Member Functions
	Stem (const Stem &o)
	Copy constructor.
Stem &	operator= (const Stem &o)
	Assignment.
	Stem (Stem &&)=default
	Move constructor.
Stem &	operator= (Stem &&)=default
	Move assignment operator.
	Stem ()
	Construct a Xapian::Stem object which doesn't change terms.
	Stem (std::string_view language, bool fallback=false)
	Construct a Xapian::Stem object for a particular language.
	Stem (StemImplementation *p)
	Construct a Xapian::Stem object with a user-provided stemming algorithm.
	~Stem ()
	Destructor.
std::string	operator() (const std::string &word) const
	Stem a word.
bool	is_none () const
	Return true if this is a no-op stemmer.
std::string	get_description () const
	Return a string describing this object.

Static Public Member Functions
static std::string	get_available_languages ()
	Return a list of available languages.

Detailed Description

Class representing a stemming algorithm.

Constructor & Destructor Documentation

Stem() [1/3]

Xapian::Stem::Stem ( )

inline

Construct a Xapian::Stem object which doesn't change terms.

Equivalent to Stem("none").

Stem() [2/3]

Xapian::Stem::Stem	(	std::string_view	language,
		bool	fallback = false )

Construct a Xapian::Stem object for a particular language.

Parameters

language

Either the English name for the language or the two letter ISO639 code.

The following language names are understood (aliases follow the name):

• none - don't stem terms
• arabic (ar) - Since Xapian 1.3.5
• armenian (hy) - Since Xapian 1.3.0
• basque (eu) - Since Xapian 1.3.0
• catalan (ca) - Since Xapian 1.3.0
• danish (da)
• dutch (nl, kraaij_pohlmann) - Before Xapian 2.0.0, "dutch" was Martin Porter's Dutch stemmer, and a stemmer which approximately implemented the Kraaij-Pohlmann Dutch stemmer was available separately as "kraaij_pohlmann".
• dutch_porter - This was the "dutch" stemmer before Xapian 2.0.0. In 1.4.x for x >= 28, "dutch_porter" was an alias for dutch to provide forward compatibility to Xapian 2.
• english (en) - Martin Porter's 2002 revision of his stemmer
• earlyenglish - English stemmer with additional rules to improve handling of Early Modern English (e.g. Shakespeare, Dickens) but these overstem some words in contemporary English (since Xapian 1.3.2; originally this was based on "porter", since Xapian 2.0.0 this is based on "english").
• lovins - Lovin's English stemmer
• porter - Porter's English stemmer exactly matching his 1980 paper
• esperanto (eo) - Since Xapian 2.0.0
• estonian (et) - Since Xapian 2.0.0
• finnish (fi)
• french (fr)
• german (de, german2) - Before Xapian 2.0.0, german2 was a separate variant of the german stemmer which normalised umlauts (e.g. ä and ae). The two variants have now been merged into one.
• greek (el) - Since Xapian 2.0.0
• hindi (hi) - Since Xapian 2.0.0
• hungarian (hu)
• indonesian (id) - Since Xapian 1.4.6
• irish (ga) - Since Xapian 1.4.7
• italian (it)
• lithuanian (lt) - Since Xapian 1.4.7
• nepali (ne) - Since Xapian 1.4.7
• norwegian (nb, nn, no)
• polish (pl) - Since Xapian 2.0.0
• portuguese (pt)
• romanian (ro)
• russian (ru)
• serbian (sr) - Since Xapian 2.0.0
• spanish (es)
• swedish (sv)
• tamil (ta) - Since Xapian 1.4.7
• turkish (tr)
• yiddish (yi) - Since Xapian 2.0.0

Parameters

fallback

If true then treat unknown language as "none", otherwise an exception is thrown (default: false). Parameter added in Xapian 1.4.14 - older versions always threw an exception.

Exceptions

Xapian::InvalidArgumentError

is thrown if language isn't recognised and fallback is false.

Stem() [3/3]

Xapian::Stem::Stem ( StemImplementation * p )

inlineexplicit

Construct a Xapian::Stem object with a user-provided stemming algorithm.

You can subclass Xapian::StemImplementation to implement your own stemming algorithm (or to wrap a third-party algorithm) and then wrap your implementation in a Xapian::Stem object to pass to the Xapian API.

Parameters

p	The user-subclassed StemImplementation object. This is reference counted, and so will be automatically deleted by the Xapian::Stem wrapper when no longer required.

Member Function Documentation

get_available_languages()

std::string Xapian::Stem::get_available_languages ( )

inlinestatic

Return a list of available languages.

Each stemmer is only included once in the list (not once for each alias). The name included is the English name of the language.

The list is returned as a string, with language names separated by spaces. This is a static method, so a Xapian::Stem object is not required for this operation.

operator()()

std::string Xapian::Stem::operator() ( const std::string & word ) const

inline

Stem a word.

Parameters

word	a word to stem.

Returns

the stem

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

• xapian/stem.h