lutf8proc is a Lua 5.3 binding of some of the functions from the utf8proc library. I created it for fun so it isn't well tested and its behavior isn't set in stone. I mainly use the normalization functions. See the testcases for examples.
These take either a string or a number (which is interpreted as a code point). They currently allow any length of string, but only return information on the first character.
utf8proc.cat
Returns the code for the General Category of a code point.
utf8proc.cat "a", utf8proc.cat(0x61) --> "Ll", "Ll"
utf8proc.catdesc
Returns a long name of the General Category of a code point.
utf8proc.catdesc "a", utf8proc.catdesc(0x61) --> "Letter, lowercase", "Letter, lowercase"
utf8proc.valid(code_point)
Returns true if a codepoint is valid, false if not. Checks that it is below 0x10FFFF and not a surrogate codepoint.
These take and return a string.
utf8proc.comp, utf8proc.decomp, utf8proc.ccomp, utf8proc.cdecomp
Returns a composed (NFC), decomposed (NFD), compatibility composed (NFKC), or compatibility decomposed (NFKD) version of a string.
utf8proc.decomp "á" --> "á" (U+00E1 -> U+0061 U+0301)
utf8proc.comp "á" --> "á" (U+0061 U+0301 -> U+00E1)
utf8proc.normalize(str, normalization)
Returns a normalized form of a string. Generalized version of the functions above. normalization is case-insensitive. For instance, utf8proc.normalize("á", "nfd") and utf8proc.normalize("á", "NFD") are both equivalent to utf8proc.decomp "á".
utf8proc.lower, utf8proc.upper, utf8proc.title
Returns a lowercase, uppercase, or titlecase version of a string. There are only a few code points for which titlecase is different from uppercase.
utf8proc.map(str, options) (bit-flag options) or utf8proc.map(str, option1[, option2, ...]) (string options)
Transform a string in a custom way. Options are either numbers (bit flags) or strings depending on how you compile the library. String options are case-insensitive.
Bit flags:
local options = utf8proc.options()
utf8proc.map("αὐτός", options.stripmark | options.decompose | options.casefold) --> "αυτοσ"
Strings:
utf8proc.map("αὐτός", "stripmark", "decompose", "casefold") --> "αυτοσ"
utf8proc.map("αὐτός", "STRIPMARK", "DECOMPOSE", "CASEFOLD") --> "αυτοσ"
utf8proc.map_custom(str, options, function) (bit-flag options) or utf8proc.map_custom(str, function[, option1[, option2, ...]]) (string options)
Apply a function to each codepoint in a string.
utf8proc.map_custom("abc", function (cp) return cp - 0x20 end) --> "ABC"
utf8proc.interpret_options(options) (bit-flag options)
Returns the list of string names for an integer. Throws an error if the integer contains bits that do not correspond to a flag.