Unicod...malize(3perl)

📦
version 5.44.0 · 14 versions
, in arch rolling

okay so bestie, this is Unicode::Normalize(3perl) from the Perl Programmers Reference Guide, and it's literally the Unicode Normalization Forms module. 💅✨

🌸 NAME 🌸

Unicode::Normalize — Unicode Normalization Forms. That's the whole vibe. It normalizes Unicode strings, no cap. 🎀

✨ SYNOPSIS ✨

Two ways to pull up, bestie:

(1) using function names exported by default:

use Unicode::Normalize;

$NFD_string  = NFD($string);  # Normalization Form D
$NFC_string  = NFC($string);  # Normalization Form C
$NFKD_string = NFKD($string); # Normalization Form KD
$NFKC_string = NFKC($string); # Normalization Form KC

(2) using function names exported on request:

use Unicode::Normalize 'normalize';

$NFD_string  = normalize('D',  $string);  # Normalization Form D
$NFC_string  = normalize('C',  $string);  # Normalization Form C
$NFKD_string = normalize('KD', $string);  # Normalization Form KD
$NFKC_string = normalize('KC', $string);  # Normalization Form KC

🔥 DESCRIPTION 🔥

Okay so parameters first, because we love clarity:

  • $string — used as a string under character semantics (see perlunicode). So like, it's in character mode, bestie. 🧠✨
  • $code_point — should be an unsigned integer representing a Unicode code point. It's giving "number that points at a character," periodt.
Note: Between XSUB and pure Perl, there is an incompatibility about the interpretation of $code_point as a decimal number. XSUB converts $code_point to an unsigned integer, but pure Perl does not. Do not use a floating point nor a negative sign in $code_point. 💀

💅 Normalization Forms 💅

$NFD_string = NFD($string)

It returns the Normalization Form D (formed by canonical decomposition). Slay.

$NFC_string = NFC($string)

It returns the Normalization Form C (formed by canonical decomposition followed by canonical composition). Iconic.

$NFKD_string = NFKD($string)

It returns the Normalization Form KD (formed by compatibility decomposition). Ate.

$NFKC_string = NFKC($string)

It returns the Normalization Form KC (formed by compatibility decomposition followed by canonical composition). 💅

$FCD_string = FCD($string)

If the given string is in FCD ("Fast C or D" form; cf. UTN #5), it returns the string without modification; otherwise it returns an FCD string.

Note: FCD is not always unique, then plural forms may be equivalent each other. FCD() will return one of these equivalent forms.

$FCC_string = FCC($string)

It returns the FCC form ("Fast C Contiguous"; cf. UTN #5).

Note: FCC is unique, as well as four normalization forms (NF*).

$normalized_string = normalize($form_name, $string)

It returns the normalization form of $form_name.

As $form_name, one of the following names must be given.

'C'  or 'NFC'  for Normalization Form C  (UAX #15)
'D'  or 'NFD'  for Normalization Form D  (UAX #15)
'KC' or 'NFKC' for Normalization Form KC (UAX #15)
'KD' or 'NFKD' for Normalization Form KD (UAX #15)

'FCD'          for "Fast C or D" Form  (UTN #5)
'FCC'          for "Fast C Contiguous" (UTN #5)

🦋 Decomposition and Composition 🦋

$decomposed_string = decompose($string [, $useCompatMapping])

It returns the concatenation of the decomposition of each character in the string.

If the second parameter (a boolean) is omitted or false, the decomposition is canonical decomposition; if the second parameter (a boolean) is true, the decomposition is compatibility decomposition.

The string returned is not always in NFD/NFKD. Reordering may be required.

$NFD_string  = reorder(decompose($string));       # eq. to NFD()
$NFKD_string = reorder(decompose($string, TRUE)); # eq. to NFKD()

$reordered_string = reorder($string)

It returns the result of reordering the combining characters according to Canonical Ordering Behavior.

For example, when you have a list of NFD/NFKD strings, you can get the concatenated NFD/NFKD string from them, by saying

$concat_NFD  = reorder(join '', @NFD_strings);
$concat_NFKD = reorder(join '', @NFKD_strings);

$composed_string = compose($string)

It returns the result of canonical composition without applying any decomposition.

For example, when you have a NFD/NFKD string, you can get its NFC/NFKC string, by saying

$NFC_string  = compose($NFD_string);
$NFKC_string = compose($NFKD_string);

($processed, $unprocessed) = splitOnLastStarter($normalized)

It returns two strings: the first one, $processed, is a part before the last starter, and the second one, $unprocessed is another part after the first part. A starter is a character having a combining class of zero (see UAX #15).

Note that $processed may be empty (when $normalized contains no starter or starts with the last starter), and then $unprocessed should be equal to the entire $normalized.

When you have a $normalized string and an $unnormalized string following it, a simple concatenation is wrong:

$concat = $normalized . normalize($form, $unnormalized); # wrong!

Instead of it, do like this:

($processed, $unprocessed) = splitOnLastStarter($normalized);
$concat = $processed . normalize($form,$unprocessed.$unnormalized);

splitOnLastStarter() should be called with a pre-normalized parameter $normalized, that is in the same form as $form you want.

If you have an array of @string that should be concatenated and then normalized, you can do like this:

my $result = "";
my $unproc = "";
foreach my $str (@string) {
    $unproc .= $str;
    my $n = normalize($form, $unproc);
    my($p, $u) = splitOnLastStarter($n);
    $result .= $p;
    $unproc  = $u;
}
$result .= $unproc;
# instead of normalize($form, join('', @string))

$processed = normalize_partial($form, $unprocessed)

A wrapper for the combination of normalize() and splitOnLastStarter(). Note that $unprocessed will be modified as a side-effect.

If you have an array of @string that should be concatenated and then normalized, you can do like this:

my $result = "";
my $unproc = "";
foreach my $str (@string) {
    $unproc .= $str;
    $result .= normalize_partial($form, $unproc);
}
$result .= $unproc;
# instead of normalize($form, join('', @string))

$processed = NFD_partial($unprocessed)

It does like normalize_partial('NFD', $unprocessed). Note that $unprocessed will be modified as a side-effect.

$processed = NFC_partial($unprocessed)

It does like normalize_partial('NFC', $unprocessed). Note that $unprocessed will be modified as a side-effect.

$processed = NFKD_partial($unprocessed)

It does like normalize_partial('NFKD', $unprocessed). Note that $unprocessed will be modified as a side-effect.

$processed = NFKC_partial($unprocessed)

It does like normalize_partial('NFKC', $unprocessed). Note that $unprocessed will be modified as a side-effect.

✨ Quick Check ✨

(see Annex 8, UAX #15; and lib/unicore/DerivedNormalizationProps.txt)

The following functions check whether the string is in that normalization form.

The result returned will be one of the following:

YES     The string is in that normalization form.
NO      The string is not in that normalization form.
MAYBE   Dubious. Maybe yes, maybe no.

$result = checkNFD($string)

It returns true (1) if "YES"; false ("empty string") if "NO".

$result = checkNFC($string)

It returns true (1) if "YES"; false ("empty string") if "NO"; "undef" if "MAYBE".

$result = checkNFKD($string)

It returns true (1) if "YES"; false ("empty string") if "NO".

$result = checkNFKC($string)

It returns true (1) if "YES"; false ("empty string") if "NO"; "undef" if "MAYBE".

$result = checkFCD($string)

It returns true (1) if "YES"; false ("empty string") if "NO".

$result = checkFCC($string)

It returns true (1) if "YES"; false ("empty string") if "NO"; "undef" if "MAYBE".

Note: If a string is not in FCD, it must not be in FCC. So checkFCC($not_FCD_string) should return "NO".

$result = check($form_name, $string)

It returns true (1) if "YES"; false ("empty string") if "NO"; "undef" if "MAYBE".

As $form_name, one of the following names must be given.

'C'  or 'NFC'  for Normalization Form C  (UAX #15)
'D'  or 'NFD'  for Normalization Form D  (UAX #15)
'KC' or 'NFKC' for Normalization Form KC (UAX #15)
'KD' or 'NFKD' for Normalization Form KD (UAX #15)

'FCD'          for "Fast C or D" Form  (UTN #5)
'FCC'          for "Fast C Contiguous" (UTN #5)

📝 Note

In the cases of NFD, NFKD, and FCD, the answer must be either "YES" or "NO". The answer "MAYBE" may be returned in the cases of NFC, NFKC, and FCC.

A "MAYBE" string should contain at least one combining character or the like. For example, "COMBINING ACUTE ACCENT" has the MAYBE_NFC/MAYBE_NFKC property.

Both checkNFC("A\N{COMBINING ACUTE ACCENT}") and checkNFC("B\N{COMBINING ACUTE ACCENT}") will return "MAYBE". "A\N{COMBINING ACUTE ACCENT}" is not in NFC (its NFC is "\N{LATIN CAPITAL LETTER A WITH ACUTE}"), while "B\N{COMBINING ACUTE ACCENT}" is in NFC.

If you want to check exactly, compare the string with its NFC/NFKC/FCC.

if ($string eq NFC($string)) {
    # $string is exactly normalized in NFC;
} else {
    # $string is not normalized in NFC;
}

if ($string eq NFKC($string)) {
    # $string is exactly normalized in NFKC;
} else {
    # $string is not normalized in NFKC;
}

🧚 Character Data 🧚

These functions are interface of character data used internally. If you want only to get Unicode normalization forms, you don't need call them yourself.

$canonical_decomposition = getCanon($code_point)

If the character is canonically decomposable (including Hangul Syllables), it returns the (full) canonical decomposition as a string. Otherwise it returns "undef".

Note: According to the Unicode standard, the canonical decomposition of the character that is not canonically decomposable is same as the character itself.

$compatibility_decomposition = getCompat($code_point)

If the character is compatibility decomposable (including Hangul Syllables), it returns the (full) compatibility decomposition as a string. Otherwise it returns "undef".

Note: According to the Unicode standard, the compatibility decomposition of the character that is not compatibility decomposable is same as the character itself.
  • $code_point_composite = getComposite($code_point_here, $code_point_next) — okay so if these two characters, here and next (talking code points bestie), are composable — and yes that includes Hangul Jamo/Syllables and Composition Exclusions — it hands you back the code point of the composite. If they're not composable? You get undef. That's it, that's the whole vibe. 💀
  • $combining_class = getCombinClass($code_point) — gives you the combining class of the character, as an integer. Slay. ✨
  • $may_be_composed_with_prev_char = isComp2nd($code_point) — returns a boolean: can this char (at the codepoint you gave it) be composed with the previous one in a certain composition? Includes Hangul Compositions, but excludes Composition Exclusions and Non-Starter Decompositions. No cap. 💅
  • $is_exclusion = isExclusion($code_point) — boolean, is this code point a composition exclusion or not. 🎀
  • $is_singleton = isSingleton($code_point) — boolean, is this code point a singleton. 🦋
  • $is_non_starter_decomposition = isNonStDecomp($code_point) — boolean, does this code point have Non-Starter Decomposition. 🌸
  • $is_Full_Composition_Exclusion = isComp_Ex($code_point) — boolean of the derived property Comp_Ex (Full_Composition_Exclusion), which is literally generated from Composition Exclusions + Singletons + Non-Starter Decompositions. Iconic combo meal fr. 🔥
  • $NFD_is_NO = isNFD_NO($code_point) — boolean of the derived property NFD_NO (NFD_Quick_Check=No). ⭐
  • $NFC_is_NO = isNFC_NO($code_point) — boolean of the derived property NFC_NO (NFC_Quick_Check=No). ⭐
  • $NFC_is_MAYBE = isNFC_MAYBE($code_point) — boolean of the derived property NFC_MAYBE (NFC_Quick_Check=Maybe). The maybe of it all, honestly so real. 👑
  • $NFKD_is_NO = isNFKD_NO($code_point) — boolean of the derived property NFKD_NO (NFKD_Quick_Check=No). 🌈
  • $NFKC_is_NO = isNFKC_NO($code_point) — boolean of the derived property NFKC_NO (NFKC_Quick_Check=No). 🌈
  • $NFKC_is_MAYBE = isNFKC_MAYBE($code_point) — boolean of the derived property NFKC_MAYBE (NFKC_Quick_Check=Maybe). 💜

🫶 EXPORT 🫶

  • NFC, NFD, NFKC, NFKD — these are yours by default bestie, they come pre-loaded onto your counter. 🎀
  • normalize and other some functions — these you gotta ask for, on request only. Ask nicely. 💖

😭 CAVEATS 😭

Okay this is the part where I hold your hand fr fr because it gets real.

🦋 Perl's version vs. Unicode version 🦋

So since this module refers to perl core's Unicode database in the directory /lib/unicore (or formerly /lib/unicode), the Unicode version of normalization implemented by this module fully depends on what has been compiled into your perl. Which perl you got = which Unicode you got. Periodt.

The following table lists the default Unicode version that comes with various perl versions. And yes, it is possible to change the Unicode version in any perl version to be any earlier Unicode version — so someone could cause Unicode 3.2 to be used in any perl version starting with 5.8.0. Read $Config{privlib}/unicore/README.perl for the details. iykyk. 👑

  • perl 5.6.1 → Unicode 3.0.1
  • perl 5.7.2 → Unicode 3.1.0
  • perl 5.7.3 → Unicode 3.1.1 (normalization is same as 3.1.0)
  • perl 5.8.0 → Unicode 3.2.0
  • perl 5.8.1-5.8.3 → Unicode 4.0.0
  • perl 5.8.4-5.8.6 → Unicode 4.0.1 (normalization is same as 4.0.0)
  • perl 5.8.7-5.8.8 → Unicode 4.1.0
  • perl 5.10.0 → Unicode 5.0.0
  • perl 5.8.9, 5.10.1 → Unicode 5.1.0
  • perl 5.12.x → Unicode 5.2.0
  • perl 5.14.x → Unicode 6.0.0
  • perl 5.16.x → Unicode 6.1.0
  • perl 5.18.x → Unicode 6.2.0
  • perl 5.20.x → Unicode 6.3.0
  • perl 5.22.x → Unicode 7.0.0

🙈 Correction of decomposition mapping 🙈

So in older Unicode versions, a small number of characters (all of which are CJK compatibility ideographs as far as they have been found — clocked them, they're the suspects 💀) may have an erroneous decomposition mapping. See lib/unicore/NormalizationCorrections.txt for receipts.

Anyhow, this module will neither refer to lib/unicore/NormalizationCorrections.txt nor provide any specific version of normalization. So this module running on an older perl with an older Unicode database may use the erroneous decomposition mapping blindly, fully conforming to the Unicode database. Not me calling it "blindly" but okay, that's literally the situation. 😭

🧚 Revised definition of canonical composition 🧚

In Unicode 4.1.0, the definition D2 of canonical composition (which affects NFC and NFKC) has been changed — see Public Review Issue #29 and recent UAX #15.

This module has used the newer definition since the version 0.07 (Oct 31, 2001). And this module will not support the normalization according to the older definition, even if the Unicode version implemented by perl is lower than 4.1.0. Newer definition only, no retro vibes. 💅

👑 AUTHOR 👑

SADAHIRO Tomoyuki <SADAHIRO@cpan.org>

Currently maintained by <perl5-porters@perl.org>

Copyright(C) 2001-2012, SADAHIRO Tomoyuki. Japan. All rights reserved.

🌸 LICENSE 🌸

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. Slay, open source. 💖

⭐ SEE ALSO ⭐

And that's the whole page bestie, we made it. 🎉 This whole thing ships courtesy of perl v5.44.0, dated 2026-10-17 — that's your source and version and date, cute little timestamp for the archives. Go normalize something. 💅✨

📦 where this page comes from