text: // Copyright 2017 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // Package language implements BCP 47 language tags and related functionality.
  //
  // The most important function of package language is to match a list of
  // user-preferred languages to a list of supported languages.
  // It alleviates the developer of dealing with the complexity of this process
  // and provides the user with the best experience
  // (see https://blog.golang.org/matchlang).
  //
  //
  // Matching preferred against supported languages
  //
  // A Matcher for an application that supports English, Australian English,
  // Danish, and standard Mandarin can be created as follows:
  //
  //    var matcher = language.NewMatcher([]language.Tag{
  //        language.English,   // The first language is used as fallback.
  //        language.MustParse("en-AU"),
  //        language.Danish,
  //        language.Chinese,
  //    })
  //
  // This list of supported languages is typically implied by the languages for
  // which there exists translations of the user interface.
  //
  // User-preferred languages usually come as a comma-separated list of BCP 47
  // language tags.
  // The MatchString finds best matches for such strings:
  //
  //    handler(w http.ResponseWriter, r *http.Request) {
  //        lang, _ := r.Cookie("lang")
  //        accept := r.Header.Get("Accept-Language")
  //        tag, _ := language.MatchStrings(matcher, lang.String(), accept)
  //
  //        // tag should now be used for the initialization of any
  //        // locale-specific service.
  //    }
  //
  // The Matcher's Match method can be used to match Tags directly.
  //
  // Matchers are aware of the intricacies of equivalence between languages, such
  // as deprecated subtags, legacy tags, macro languages, mutual
  // intelligibility between scripts and languages, and transparently passing
  // BCP 47 user configuration.
  // For instance, it will know that a reader of Bokmål Danish can read Norwegian
  // and will know that Cantonese ("yue") is a good match for "zh-HK".
  //
  //
  // Using match results
  //
  // To guarantee a consistent user experience to the user it is important to
  // use the same language tag for the selection of any locale-specific services.
  // For example, it is utterly confusing to substitute spelled-out numbers
  // or dates in one language in text of another language.
  // More subtly confusing is using the wrong sorting order or casing
  // algorithm for a certain language.
  //
  //    All the packages in x/text that provide locale-specific services
  //    (e.g. collate, cases) should be initialized with the tag that was
  //    obtained at the start of an interaction with the user.
  //
  // Note that Tag that is returned by Match and MatchString may differ from any
  // of the supported languages, as it may contain carried over settings from
  // the user tags.
  // This may be inconvenient when your application has some additional
  // locale-specific data for your supported languages.
  // Match and MatchString both return the index of the matched supported tag
  // to simplify associating such data with the matched tag.
  //
  //
  // Canonicalization
  //
  // If one uses the Matcher to compare languages one does not need to
  // worry about canonicalization.
  //
  // The meaning of a Tag varies per application. The language package
  // therefore delays canonicalization and preserves information as much
  // as possible. The Matcher, however, will always take into account that
  // two different tags may represent the same language.
  //
  // By default, only legacy and deprecated tags are converted into their
  // canonical equivalent. All other information is preserved. This approach makes
  // the confidence scores more accurate and allows matchers to distinguish
  // between variants that are otherwise lost.
  //
  // As a consequence, two tags that should be treated as identical according to
  // BCP 47 or CLDR, like "en-Latn" and "en", will be represented differently. The
  // Matcher handles such distinctions, though, and is aware of the
  // equivalence relations. The CanonType type can be used to alter the
  // canonicalization form.
  //
  // References
  //
  // BCP 47 - Tags for Identifying Languages http://tools.ietf.org/html/bcp47
  //
  package language // import "golang.org/x/text/language"
  
  // TODO: explanation on how to match languages for your own locale-specific
  // service.
  