BCP-47 compliant language tag predicates (original) (raw)

1.0

This module provides a single predicate that determines whether a given string is a valid Language Tag as defined by RFC5646 and used across HTTP, HTML, XML, RDF, and much more.

References

• BCP-47, RFC5646 Tags for Identifying Languages
• IANA Registry of Language Tags (Assigned)
• IANA Registry of Language Subtags
• IANA Registry of Language Tag Extensions (UCD)

Returns #t if the string val is a valid BCP-47 language tag.

Examples:

> (require langtag)
> (language-tag? "en")
#t
> (language-tag? "en-US")
#t
> (language-tag? "en-US-boont")
#t
> (language-tag? "en-Latn-US")
#t
> (language-tag? "i-klingon")
#t
> (language-tag? "x-private")
#t

1 Components🔗ℹ

Returns #t if the string val corresponds to one of the three top-level productions for the rule Language-Tag.

Examples:

Returns #t if the string val corresponds to one of the components of a normal-use language tag.

2 Matching🔗ℹ

TBD

Examples:

> (require langtag)
> (language-tag-match "en")
'(lang "en" ((language . "en")))
> (language-tag-match "en-US")
'(lang "en-US" ((language . "en") (region . "US")))
> (language-tag-match "en-US-boont")
'(lang "en-US-boont" ((language . "en") (region . "US") (variant . "boont")))
> (language-tag-match "en-Latn-US")
'(lang "en-Latn-US" ((language . "en") (script . "Latn") (region . "US")))
> (language-tag-match "i-klingon")
'(grandfathered-i "i-klingon")
> (language-tag-match "x-private")
'(private-use "x-private")

3 Appendix: Definition🔗ℹ

The syntax of the language tag, from [RFC5646], in ABNF [RFC5234] is: