Does there exist a standard Perl module or function that, given a Unicode Combining Character Sequence (or, more generally, an arbitrary Unicode text string), will generate a list of all canonically equivalent strings?
For example, if given the character U+1EAD, I'd like to get back a list of all these canonically equivalent sequences:
0061 0302 0323
0061 0323 0302
00E2 0323
1EA1 0302
1EAD
(I don't particularly care whether the interface is in terms of arrays of USVs or utf strings.)
Is this an XY problem? If you want to compare/match 2 unicode strings and you're worried that different ways of encoding the accented characters would create false negatives, then the best way to do this would be to normalize the 2 strings using one of the normalization functions from Unicode::Normalize, before doing the comparison or match.
Otherwise it gets a little messy.
You could get the complete character name using charnames::viacode(0x1EAD); (for U+1EAD it would be LATIN SMALL LETTER A WITH CIRCUMFLEX AND DOT BELOW), and get the various composing characters by splitting the name on WITH|AND. Then you could generate all combinations (checking that they exist!) of the base character + modifiers and the other modifiers. At this point you will run into the problem of matching the combining characters names in the full name (eg CIRCUMFLEX) with the combining character real name (COMBINING CIRCUMFLEX ACCENT). There are probably rules for this, but I don't know them.
This would be my naive attempt, there may be better ways of doing this, but since so far no one has volunteered the information...
Related
What is the likelihood that I'll run into COMBINING LATIN SMALL LETTER C (U+0368) in "real life" (besides clever Scottish folk)?
I'm asking since it's in both the Unicode Block Combining Diacritical Marks and the Category Mark, Nonspacing [Mn].
As a result, it seems to gets treated the same as characters such as COMBINING GRAVE ACCENT (U+0300) by Utilities such as the ICU Transliterator (using either the suggested "NFD; [:Nonspacing Mark:] Remove; NFC" or a straight "Latin-ASCII" transliteration).
The likelihood is very close to zero, but not exactly zero. You cannot prevent anyone from using a Unicode character as he likes. There is no specific information about U+0368 in the Unicode Standard, but it has definitely been defined as a combining character that will cause a symbol (c) to be displayed above the preceding character. I would expect to find it mostly in digitized forms of medieval manuscripts, or something like that.
Using it after a space character, as in the “clever” page mentioned, is not the intended use, but not invalid either. Unicode lets you use any combining mark after any character, whether it makes sense or not.
It has no canonical or compatibility decomposition, so there is no clear-cut way to deal with in a context where you cannot, or do not want to, retain the character.
The likelihood is utterly indeterminate except to say that if you expect it not to occur, then it will occur.
What is the subset of Unicode characters that are normally used in writing — such as those that would be typically found in a newspaper article?
For example, in English, the characters in the range [a-zA-Z0-9], plus some punctuation characters, would be sufficient for most writing.
But I want to support languages that use characters that fall outside the ASCII range, while excluding the non-printing or decorative characters.
The objective is to restrict the user input to the application to codepoints that are legitimately used in written language. Because the user input will be saved and displayed, I do not want to allow pranksters to input text consisting entirely of things like diacritics, Unicode combining characters, Unicode flow control characters, etc.
Regrettably, I am not fluent in every single language found in Unicode. Has anyone compiled a list of all of the subset of Unicode characters that are normally used in writing?
The official list of Unicode code points is UnicodeData.txt. This is a plain text file with one line per code point; it's easily machine-readable. For example:
0022;QUOTATION MARK;Po;0;ON;;;;;N;;;;;
The third semicolon-delimited field is the abbreviated name of the "General Category". This is explained further in chapter 4 of the Unicode Standard, specifically in section 4.5; see the table on page 131 (page 12 of the PDF file). For example, "Lu" is uppercase letters, "Ll" is lowercase letters, Pc, Pd, Ps, et al are various kinds of punctuation. (The first letter of the two-letter abbreviation represents a higher-level category such as letter, digit, punctuation, etc.)
Note that some ranges of code points are not listed explicitly. For example, the range of CJK (Chinese, Japanese, Korean) ideographs is represented as:
4E00;<CJK Ideograph, First>;Lo;0;L;;;;;N;;;;;
9FCC;<CJK Ideograph, Last>;Lo;0;L;;;;;N;;;;;
I think there are other files on unicode.org that fill in these gaps.
I'm still not 100% clear on just what subset you're trying to define, but you can probably define it as a particular set of General Category values.
I do not want to allow pranksters to input text consisting entirely of things like diacritics, Unicode combining characters
Diacritics/combining characters will be used in normal written language. So if you want to stop 'pranksters' you're going to need something more sophisticated than just a list of permitted characters. You'll have to do some sort of linguistic analysis for every language you want to permit.
I'd recommend not bothering with this, because it's going to be hard and you won't succeed anyway. Just let people write what they want.
Try WGL4 (652 characters), MES-1 (335 characters) or MES-2 (1062 characters). Find these at Wikipedia.
You may wish to exclude characters IJijĸĿŀʼn˚―⅛⅜⅝⅞♪ from MES-1 if you want to use this set.
Edit: I realize this is a bad answer. Especially the removing characters from MES-1 part was total garbage. I shouldn't have posted this. I'm ashamed of whoever upvoted this.
If anything, use Subset1 (678 characters), Subset2 (1193 characters) and Subset3 (2823 characters). https://unicodesubsets.miraheze.org/wiki/User:PiotrGrochowski
For combining diacritics, are they counted as letters? Since, as far as I know, they can only combine with other letters in well-formed Unicode.
The ICU function to determine if a Unicode codepoint is a letter only takes one codepoint, so for any given codepoint, it can't know if they've been combined with a diacritic- or if it's a diacritic, what it's been combined with. I'm trying to implement something akin to a Unicode-aware regex, using a construct like
while(is_letter(codepoint))
However, I'm quite concerned about what's going to happen if codepoint is actually a diacritic, which would be collated with a previous codepoint, and other collating marks.
Is this safe to do? Or will I have to explicitly find and ignore diacritics and other collating marks?
Edit: What I really need to do is iterate characters, not codepoints.
This question is a victim of the XY problem. I need to raise a question about my actual problem.
I'm not totally clear on what you're trying to do, so I apologize in advance if this isn't the answer you're looking for, but:
For combining diacritics, are they counted as letters?
Broadly speaking, diacritics are counted as "marks" rather than "letters". For example, U+0301 COMBINING ACUTE ACCENT, as in <ś>, is a "nonspacing mark", which is one of three kinds of "mark". However, the "modifier letters", which are counted as "letters", might nonetheless be thought of as diacritics; for example, U+02C0 MODIFIER LETTER GLOTTAL STOP, as in <sˀ>, is a "modifier letter".
If you look through the main file of the Unicode Character Database (warning: it's 1.3 MB text-file), you can get a sense for which characters are classified as "modifier letters" (Lm) and which as "nonspacing marks" (Mn) or "spacing marks" (Ms) or "enclosing marks" (Me).
Quoted from here:
Security may also be impacted by a characteristic of several character
encodings, including UTF-8: the "same thing" (as far as a user can
tell) can be represented by several distinct character sequences. For
instance, an e with acute accent can be represented by the precomposed
U+00E9 E ACUTE character or by the canonically equivalent sequence
U+0065 U+0301 (E + COMBINING ACUTE). Even though UTF-8 provides a
single byte sequence for each character sequence, the existence of
multiple character sequences for "the same thing" may have security
consequences whenever string matching, indexing,
Is this a hidden feature of UTF-8 that I've never tackled before?
This issue is not actually specific to UTF-8 at all. It happens with all encodings that can represent all (or at least most) Unicode codepoints.
The general idea of Unicode is to not provide so-called pre-composed characters (e.g. U+00E9 E ACUTE), instead they usually like to provide the base character (e.g. U+0065 LATIN SMALL LETTER E) and the combining character (e.g. U+0301 COMBINING ACUTE ACCENT). This has the advantage of not having to provide every possible combination as its own character.
Note: the U+xxxx notation is used to refer to unicode codepoints. It's the encoding-independent way to refer to Unicode characters.
However when Unicode was first designed an important goal was to have round-trip compatibility for existing, widely-used encodings, so some pre-composed characters were included (in fact most of the diacritic characters from the latin and related alphabets are included).
So yes (and tl;dr): in a correctly working Unicode-capable application U+00E9 should render the same way and be treated the same way as U+0065 followed by U+0301.
There's a non-trivial process called normalization that helps work with these differences by reducing a given string to one of four normal forms.
For example passing both strings (U+00E9 and U+0065 U+0301) will result in U+00E9 when using NFC and will result in U+0065 U+0301 when using NFD.
Very short and visualized example: the character "é" can either be represented using the Unicode code point U+00E9 (LATIN SMALL LETTER E WITH ACUTE, é), or the sequence U+0065 (LATIN SMALL LETTER E, e) followed by U+0301 (COMBINING ACUTE ACCENT, ´), which together look like this: é.
In UTF-8, é has the byte sequence xC3 xA9, while é has the byte sequence x65 xCC x81.
Note: Due to technical limitations this post does not contain the actual combination characters.
Actually I don't understand what it means by :
"Even though UTF-8 provides a single byte sequence for each character
sequence[...]"
What the quote wants to say is:
"Any given sequence of Unicode code points is mapped to one (and precisely one) sequence of bytes by the UTF-8 encoding." That is, UTF-8 is a bijection between sequences of (abstract) Unicode code points and bytes.
The problem, which the text wants to illustrate, is that there is no bijection between "letters of a text" (as commonly understood) and Unicode code points, because the same text can be represented by different sequences of Unicode code points (as explained in the example).
Actually, this has nothing to do with UTF-8 specifically; it is a fundamental property of Unicode: Many texts have more than one representations as Unicode code points. This is important to keep in mind when comparing texts expressed in Unicode (no matter in what encoding).
One (partial) solution to this is normalization. It defines various Normal forms for Unicode text, which are unique representations of a text.
Can anybody please tell me what is the range of Unicode printable characters? [e.g. Ascii printable character range is \u0020 - \u007f]
See, http://en.wikipedia.org/wiki/Unicode_control_characters
You might want to look especially at C0 and C1 control character http://en.wikipedia.org/wiki/C0_and_C1_control_codes
The wiki says, the C0 control character is in the range U+0000—U+001F and U+007F (which is the same range as ASCII) and C1 control character is in the range U+0080—U+009F
other than C-control character, Unicode also has hundreds of formatting control characters, e.g. zero-width non-joiner, which makes character spacing closer, or bidirectional text control. This formatting control characters are rather scattered.
More importantly, what are you doing that requires you to know Unicode's non-printable characters? More likely than not, whatever you're trying to do is the wrong approach to solve your problem.
This is an old question, but it is still valid and I think there is more to usefully, but briefly, say on the subject than is covered by existing answers.
Unicode
Unicode defines properties for characters.
One of these properties is "General Category" which has Major classes and subclasses. The Major classes are Letter, Mark, Punctuation, Symbol, Separator, and Other.
By knowing the properties of your characters, you can decide whether you consider them printable in your particular context.
You must always remember that terms like "character" and "printable" are often difficult and have interesting edge-cases.
Programming Language support
Some programming languages assist with this problem.
For example, the Go language has a "unicode" package which provides many useful Unicode-related functions including these two:
func IsGraphic(r rune) bool
IsGraphic reports whether the rune is defined as a Graphic by Unicode. Such
characters include letters, marks, numbers, punctuation, symbols, and spaces,
from categories L, M, N, P, S, Zs.
func IsPrint(r rune) bool
IsPrint reports whether the rune is defined as printable by Go. Such
characters include letters, marks, numbers, punctuation, symbols, and
the ASCII space character, from categories L, M, N, P, S and the ASCII
space character. This categorization is the same as IsGraphic except
that the only spacing character is ASCII space, U+0020.
Notice that it says "defined as printable by Go" not by "defined as printable by Unicode". It is almost as if there are some depths the wizards at Unicode dare not plumb.
Printable
The more you learn about Unicode, the more you realise how unexpectedly diverse and unfathomably weird human writing systems are.
In particular whether a particular "character" is printable is not always obvious.
Is a zero-width space printable? When is a hyphenation point printable? Are there characters whose printability depends on their position in a word or on what characters are adjacent to them? Is a combining-character always printable?
Footnotes
ASCII printable character range is \u0020 - \u007f
No it isn't. \u007f is DEL which is not normally considered a printable character. It is, for example, associated with the keyboard key labelled "DEL" whose earliest purpose was to command the deletion of a character from some medium (display, file etc).
In fact many 8-bit character sets have many non-consecutive ranges which are non-printable. See for example C0 and C1 controls.
First, you should remove the word 'UTF8' in your question, it's not pertinent (UTF8 is just one of the encodings of Unicode, it's something orthogonal to your question).
Second: the meaning of "printable/non printable" is less clear in Unicode. Perhaps you mean a "graphical character" ; and one can even dispute if a space is printable/graphical. The non-graphical characters would consist, basically, of control characters: the range 0x00-0x0f plus some others that are scattered.
Anyway, the vast majority of Unicode characters (more than 200.000) are "graphical". But this certainly does not imply that they are printable in your environment.
It seems to me a bad idea, if you intend to generate a "random printable" unicode string, to try to include all "printable" characters.
What you should do is pick a font, and then generate a list of which Unicode characters have glyphs defined for your font. You can use a font library like freetype to test glyphs (test for FT_Get_Char_Index(...) != 0).
Taking the opposite approach to #HoldOffHunger, it might be easier to list the ranges of non-printable characters, and use not to test if a character is printable.
In the style of Regex (so if you wanted printable characters, place a ^):
[\u0000-\u0008\u000B-\u001F\u007F-\u009F\u2000-\u200F\u2028-\u202F\u205F-\u206F\u3000\uFEFF]
Which accounts for things like separator spaces and joiners
Note that unlike their answer which is a whitelist that ignores all non-latin languages, this blacklist wont permit non-printable characters just because they're in blocks with printable characters (their answer wholly includes Non-Latin, Language Supplement blocks as 'printable', even though it contains things like 'zero-width non-joiner'..).
Be aware though, that if using this or any other solution, for sanitation for example, you may want to do something more nuanced than a blanket replace.
Arguably in that case, non-breaking spaces should change to space, not be removed, and invisible separator should be replaced with comma conditionally.
Then there's invalid character ranges, either [yet] unused or reserved for encoding purposes, and language-specific variation selectors..
NB when using regular expressions, that you enable unicode awareness if it isn't that way by default (for javascript it's via /.../u).
You can tell if you have it correct by attempting to create the regular expression with some multi-byte character ranges.
For example, the above, plus the invalid character range \u{E0100}-\u{E01EF} in javascript:
/[\u0000-\u0008\u000B-\u001F\u007F-\u009F\u2000-\u200F\u2028-\u202F\u205F-\u206F\u3000\uFEFF\u{E0100}-\u{E01EF}]/u
Without u \u{E0100}-\u{E01EF} equates to \uDB40(\uDD00-\uDB40)\uDDEF, not (\uDB40\uDD00)-(\uDB40\uDDEF), and if replacing you should always enable u even when not including multbyte unicode in the regex itself as you might break surrogate pairs that exist in the text.
What characters are valid?
At present, Unicode is defined as starting from U+0000 and ending at U+10FFFF. The first block, Basic Latin, spans U+0000 to U+007F and the last block, Supplementary Private Use Area-B, spans U+100000 to 10FFFF. If you want to see all of these blocks, see here: Wikipedia.org: Unicode Block; List of Blocks.
Let's break down what's valid/invalid in the Latin Block1.
The Latin Block: TLDR
If you're interested in filtering out either invisible characters, you'll want to filter out:
U+0000 to U+0008: Control
U+000E to U+001F: Device (i.e., Control)
U+007F: Delete (Control)
U+008D to U+009F: Device (i.e., Control)
The Latin Block: Full Ranges
Here's the Latin block, broken up into smaller sections...
U+0000 to U+0008: Control
U+0009 to U+000C: Space
U+000E to U+001F: Device (i.e., Control)
U+0020: Space
U+0021 to U+002F: Symbols
U+0030 to U+0039: Numbers
U+003A to U+0040: Symbols
U+0041 to U+005A: Uppercase Letters
U+005B to U+0060: Symbols
U+0061 to U+007A: Lowercase Letters
U+007B to U+007E: Symbols
U+007F: Delete (Control)
U+0080 to U+008C: Latin1-Supplement symbols.
U+008D to U+009F: Device (i.e., Control)
U+00A0: Non-breaking space. (i.e., )
U+00A1 to U+00BF: Symbols.
U+00C0 to U+00FF: Accented characters.
The Other Blocks
Unicode is famous for supporting non-Latin character sets, so what are these other blocks? This is just a broad overview, see the wikipedia.org page for the full, complete list.
Latin1 & Latin1-Related Blocks
U+0000 to U+007F : Basic Latin
U+0080 to U+00FF : Latin-1 Supplement
U+0100 to U+017F : Latin Extended-A
U+0180 to U+024F : Latin Extended-B
Combinable blocks
U+0250 to U+036F: 3 Blocks.
Non-Latin, Language blocks
U+0370 to U+1C7F: 55 Blocks.
Non-Latin, Language Supplement blocks
U+1C80 to U+209F: 11 Blocks.
Symbol blocks
U+20A0 to U+2BFF: 22 Blocks.
Ancient Language blocks
U+2C00 to U+2C5F: 1 Block (Glagolitic).
Language Extensions blocks
U+2C60 to U+FFEF: 66 Blocks.
Special blocks
U+FFF0 to U+FFFF: 1 Block (Specials).
One approach is to render each character to a texture and manually check if it is visible. This solution excludes spaces.
I've written such a program and used it to determine there are roughly 467241 printable characters within the first 471859 code points. I've selected this number because it covers all of the first 4 Planes of Unicode, which seem to contain all printable characters. See https://en.wikipedia.org/wiki/Plane_(Unicode)
I would much like to refine my program to produce the list of ranges, but for now here's what I am working with for anyone who needs immediate answers:
https://editor.p5js.org/SamyBencherif/sketches/_OE8Y3kS9
I am posting this tool because I think this question attracts a lot of people who are looking for slightly different applications of knowing printable ranges. Hopefully this is useful, even though it does not fully answer the question.
The printable Unicode character range, excluding the hex, is 32 to 126 in the int datatype.
Unicode, stict term, has no range. Numbers can go infinite.
What you gave is not UTF8 which has 1 byte for ASCII characters.
As for the range, I believe there is no range of printable characters. It always evolves. Check the page I gave above.