| // 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. |