## Unicode for X-double bar

U+0304 is the combining macron. There is a "combining double overline" at U+033F which might work for you, and a "combining double macron" at U+035E. Neither of these looks very clearly like a double bar in my browser. But if they work for you, the code would be something like `̿x`

which renders as ̿x or `͞x`

which renders as ͞x (This is HTML markup, not Unicode.) Note also that the combining character should go before the character it combines with, not after.

See also http://www.fileformat.info/info/unicode/block/combining_diacritical_marks/list.htm

## Double bar in plot axis annotation (e.g. ||k|| )?

You can use Unicode symbol 2016:

`plot(1:10,1:10,xlab=expression("\u2016"*x*"\u2016"))`

This works for me with X11 graphics under Ubuntu with an en_CA.utf8 locale, but you might have some trouble getting it exported portably under PDF etc. (maybe try the PDF driver from the `Cairo`

package ...). An alternative would be to use TikZ, but that has a lot of overhead too ...

## List of all unicode's open/close brackets?

There is a plain-text database of information about every Unicode character available from the Unicode Consortium; the format is described in Unicode Annex #44. The primary information is contained in UnicodeData.txt. Open and close punctuation characters are denoted with `Ps`

(punctuation start) and `Pe`

(punctuation end) in the General_Category field (the third field, delimited by `;`

). Look for those character, and you'll find what you're looking for.

Note that not all characters that you consider brackets may be listed; for instance, quotation marks (including "«»"). are indicated with `Pi`

and `Pf`

(initial and final punctuation), so you might want to include those as well. And some character, like `<`

and `>`

, are used as brackets in some contexts (such as HTML/XML), while they are considered math symbols (`Sm`

) in UnicodeData.txt. Those you are going to have to find by hand; there is no pre-determined listing of those.

Here's a quick Bash script to get this information, and its output. I've included both brackets and quotes. (note: on some Bash implementations UTF-8 printing has a bug that causes it to print U+00AB "«" and U+00BB "»" as "?", and some terminals don't have the ability to render all characters correctly.)

`while IFS=';' read number name category rest`

do

if [[ "$category" =~ Ps|Pe|Pi|Pf ]]

then

printf "%s (U+%s, %s): \u"$number"\n" "$name" "$number" "$category"

fi

done <UnicodeData.txt

LEFT PARENTHESIS (U+0028, Ps): (

RIGHT PARENTHESIS (U+0029, Pe): )

LEFT SQUARE BRACKET (U+005B, Ps): [

RIGHT SQUARE BRACKET (U+005D, Pe): ]

LEFT CURLY BRACKET (U+007B, Ps): {

RIGHT CURLY BRACKET (U+007D, Pe): }

LEFT-POINTING DOUBLE ANGLE QUOTATION MARK (U+00AB, Pi): «

RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK (U+00BB, Pf): »

TIBETAN MARK GUG RTAGS GYON (U+0F3A, Ps): ༺

TIBETAN MARK GUG RTAGS GYAS (U+0F3B, Pe): ༻

TIBETAN MARK ANG KHANG GYON (U+0F3C, Ps): ༼

TIBETAN MARK ANG KHANG GYAS (U+0F3D, Pe): ༽

OGHAM FEATHER MARK (U+169B, Ps): ᚛

OGHAM REVERSED FEATHER MARK (U+169C, Pe): ᚜

LEFT SINGLE QUOTATION MARK (U+2018, Pi): ‘

RIGHT SINGLE QUOTATION MARK (U+2019, Pf): ’

SINGLE LOW-9 QUOTATION MARK (U+201A, Ps): ‚

SINGLE HIGH-REVERSED-9 QUOTATION MARK (U+201B, Pi): ‛

LEFT DOUBLE QUOTATION MARK (U+201C, Pi): “

RIGHT DOUBLE QUOTATION MARK (U+201D, Pf): ”

DOUBLE LOW-9 QUOTATION MARK (U+201E, Ps): „

DOUBLE HIGH-REVERSED-9 QUOTATION MARK (U+201F, Pi): ‟

SINGLE LEFT-POINTING ANGLE QUOTATION MARK (U+2039, Pi): ‹

SINGLE RIGHT-POINTING ANGLE QUOTATION MARK (U+203A, Pf): ›

LEFT SQUARE BRACKET WITH QUILL (U+2045, Ps): ⁅

RIGHT SQUARE BRACKET WITH QUILL (U+2046, Pe): ⁆

SUPERSCRIPT LEFT PARENTHESIS (U+207D, Ps): ⁽

SUPERSCRIPT RIGHT PARENTHESIS (U+207E, Pe): ⁾

SUBSCRIPT LEFT PARENTHESIS (U+208D, Ps): ₍

SUBSCRIPT RIGHT PARENTHESIS (U+208E, Pe): ₎

LEFT-POINTING ANGLE BRACKET (U+2329, Ps): 〈

RIGHT-POINTING ANGLE BRACKET (U+232A, Pe): 〉

MEDIUM LEFT PARENTHESIS ORNAMENT (U+2768, Ps): ❨

MEDIUM RIGHT PARENTHESIS ORNAMENT (U+2769, Pe): ❩

MEDIUM FLATTENED LEFT PARENTHESIS ORNAMENT (U+276A, Ps): ❪

MEDIUM FLATTENED RIGHT PARENTHESIS ORNAMENT (U+276B, Pe): ❫

MEDIUM LEFT-POINTING ANGLE BRACKET ORNAMENT (U+276C, Ps): ❬

MEDIUM RIGHT-POINTING ANGLE BRACKET ORNAMENT (U+276D, Pe): ❭

HEAVY LEFT-POINTING ANGLE QUOTATION MARK ORNAMENT (U+276E, Ps): ❮

HEAVY RIGHT-POINTING ANGLE QUOTATION MARK ORNAMENT (U+276F, Pe): ❯

HEAVY LEFT-POINTING ANGLE BRACKET ORNAMENT (U+2770, Ps): ❰

HEAVY RIGHT-POINTING ANGLE BRACKET ORNAMENT (U+2771, Pe): ❱

LIGHT LEFT TORTOISE SHELL BRACKET ORNAMENT (U+2772, Ps): ❲

LIGHT RIGHT TORTOISE SHELL BRACKET ORNAMENT (U+2773, Pe): ❳

MEDIUM LEFT CURLY BRACKET ORNAMENT (U+2774, Ps): ❴

MEDIUM RIGHT CURLY BRACKET ORNAMENT (U+2775, Pe): ❵

LEFT S-SHAPED BAG DELIMITER (U+27C5, Ps): ⟅

RIGHT S-SHAPED BAG DELIMITER (U+27C6, Pe): ⟆

MATHEMATICAL LEFT WHITE SQUARE BRACKET (U+27E6, Ps): ⟦

MATHEMATICAL RIGHT WHITE SQUARE BRACKET (U+27E7, Pe): ⟧

MATHEMATICAL LEFT ANGLE BRACKET (U+27E8, Ps): ⟨

MATHEMATICAL RIGHT ANGLE BRACKET (U+27E9, Pe): ⟩

MATHEMATICAL LEFT DOUBLE ANGLE BRACKET (U+27EA, Ps): ⟪

MATHEMATICAL RIGHT DOUBLE ANGLE BRACKET (U+27EB, Pe): ⟫

MATHEMATICAL LEFT WHITE TORTOISE SHELL BRACKET (U+27EC, Ps): ⟬

MATHEMATICAL RIGHT WHITE TORTOISE SHELL BRACKET (U+27ED, Pe): ⟭

MATHEMATICAL LEFT FLATTENED PARENTHESIS (U+27EE, Ps): ⟮

MATHEMATICAL RIGHT FLATTENED PARENTHESIS (U+27EF, Pe): ⟯

LEFT WHITE CURLY BRACKET (U+2983, Ps): ⦃

RIGHT WHITE CURLY BRACKET (U+2984, Pe): ⦄

LEFT WHITE PARENTHESIS (U+2985, Ps): ⦅

RIGHT WHITE PARENTHESIS (U+2986, Pe): ⦆

Z NOTATION LEFT IMAGE BRACKET (U+2987, Ps): ⦇

Z NOTATION RIGHT IMAGE BRACKET (U+2988, Pe): ⦈

Z NOTATION LEFT BINDING BRACKET (U+2989, Ps): ⦉

Z NOTATION RIGHT BINDING BRACKET (U+298A, Pe): ⦊

LEFT SQUARE BRACKET WITH UNDERBAR (U+298B, Ps): ⦋

RIGHT SQUARE BRACKET WITH UNDERBAR (U+298C, Pe): ⦌

LEFT SQUARE BRACKET WITH TICK IN TOP CORNER (U+298D, Ps): ⦍

RIGHT SQUARE BRACKET WITH TICK IN BOTTOM CORNER (U+298E, Pe): ⦎

LEFT SQUARE BRACKET WITH TICK IN BOTTOM CORNER (U+298F, Ps): ⦏

RIGHT SQUARE BRACKET WITH TICK IN TOP CORNER (U+2990, Pe): ⦐

LEFT ANGLE BRACKET WITH DOT (U+2991, Ps): ⦑

RIGHT ANGLE BRACKET WITH DOT (U+2992, Pe): ⦒

LEFT ARC LESS-THAN BRACKET (U+2993, Ps): ⦓

RIGHT ARC GREATER-THAN BRACKET (U+2994, Pe): ⦔

DOUBLE LEFT ARC GREATER-THAN BRACKET (U+2995, Ps): ⦕

DOUBLE RIGHT ARC LESS-THAN BRACKET (U+2996, Pe): ⦖

LEFT BLACK TORTOISE SHELL BRACKET (U+2997, Ps): ⦗

RIGHT BLACK TORTOISE SHELL BRACKET (U+2998, Pe): ⦘

LEFT WIGGLY FENCE (U+29D8, Ps): ⧘

RIGHT WIGGLY FENCE (U+29D9, Pe): ⧙

LEFT DOUBLE WIGGLY FENCE (U+29DA, Ps): ⧚

RIGHT DOUBLE WIGGLY FENCE (U+29DB, Pe): ⧛

LEFT-POINTING CURVED ANGLE BRACKET (U+29FC, Ps): ⧼

RIGHT-POINTING CURVED ANGLE BRACKET (U+29FD, Pe): ⧽

LEFT SUBSTITUTION BRACKET (U+2E02, Pi): ⸂

RIGHT SUBSTITUTION BRACKET (U+2E03, Pf): ⸃

LEFT DOTTED SUBSTITUTION BRACKET (U+2E04, Pi): ⸄

RIGHT DOTTED SUBSTITUTION BRACKET (U+2E05, Pf): ⸅

LEFT TRANSPOSITION BRACKET (U+2E09, Pi): ⸉

RIGHT TRANSPOSITION BRACKET (U+2E0A, Pf): ⸊

LEFT RAISED OMISSION BRACKET (U+2E0C, Pi): ⸌

RIGHT RAISED OMISSION BRACKET (U+2E0D, Pf): ⸍

LEFT LOW PARAPHRASE BRACKET (U+2E1C, Pi): ⸜

RIGHT LOW PARAPHRASE BRACKET (U+2E1D, Pf): ⸝

LEFT VERTICAL BAR WITH QUILL (U+2E20, Pi): ⸠

RIGHT VERTICAL BAR WITH QUILL (U+2E21, Pf): ⸡

TOP LEFT HALF BRACKET (U+2E22, Ps): ⸢

TOP RIGHT HALF BRACKET (U+2E23, Pe): ⸣

BOTTOM LEFT HALF BRACKET (U+2E24, Ps): ⸤

BOTTOM RIGHT HALF BRACKET (U+2E25, Pe): ⸥

LEFT SIDEWAYS U BRACKET (U+2E26, Ps): ⸦

RIGHT SIDEWAYS U BRACKET (U+2E27, Pe): ⸧

LEFT DOUBLE PARENTHESIS (U+2E28, Ps): ⸨

RIGHT DOUBLE PARENTHESIS (U+2E29, Pe): ⸩

LEFT ANGLE BRACKET (U+3008, Ps): 〈

RIGHT ANGLE BRACKET (U+3009, Pe): 〉

LEFT DOUBLE ANGLE BRACKET (U+300A, Ps): 《

RIGHT DOUBLE ANGLE BRACKET (U+300B, Pe): 》

LEFT CORNER BRACKET (U+300C, Ps): 「

RIGHT CORNER BRACKET (U+300D, Pe): 」

LEFT WHITE CORNER BRACKET (U+300E, Ps): 『

RIGHT WHITE CORNER BRACKET (U+300F, Pe): 』

LEFT BLACK LENTICULAR BRACKET (U+3010, Ps): 【

RIGHT BLACK LENTICULAR BRACKET (U+3011, Pe): 】

LEFT TORTOISE SHELL BRACKET (U+3014, Ps): 〔

RIGHT TORTOISE SHELL BRACKET (U+3015, Pe): 〕

LEFT WHITE LENTICULAR BRACKET (U+3016, Ps): 〖

RIGHT WHITE LENTICULAR BRACKET (U+3017, Pe): 〗

LEFT WHITE TORTOISE SHELL BRACKET (U+3018, Ps): 〘

RIGHT WHITE TORTOISE SHELL BRACKET (U+3019, Pe): 〙

LEFT WHITE SQUARE BRACKET (U+301A, Ps): 〚

RIGHT WHITE SQUARE BRACKET (U+301B, Pe): 〛

REVERSED DOUBLE PRIME QUOTATION MARK (U+301D, Ps): 〝

DOUBLE PRIME QUOTATION MARK (U+301E, Pe): 〞

LOW DOUBLE PRIME QUOTATION MARK (U+301F, Pe): 〟

ORNATE LEFT PARENTHESIS (U+FD3E, Ps): ﴾

ORNATE RIGHT PARENTHESIS (U+FD3F, Pe): ﴿

PRESENTATION FORM FOR VERTICAL LEFT WHITE LENTICULAR BRACKET (U+FE17, Ps): ︗

PRESENTATION FORM FOR VERTICAL RIGHT WHITE LENTICULAR BRAKCET (U+FE18, Pe): ︘

PRESENTATION FORM FOR VERTICAL LEFT PARENTHESIS (U+FE35, Ps): ︵

PRESENTATION FORM FOR VERTICAL RIGHT PARENTHESIS (U+FE36, Pe): ︶

PRESENTATION FORM FOR VERTICAL LEFT CURLY BRACKET (U+FE37, Ps): ︷

PRESENTATION FORM FOR VERTICAL RIGHT CURLY BRACKET (U+FE38, Pe): ︸

PRESENTATION FORM FOR VERTICAL LEFT TORTOISE SHELL BRACKET (U+FE39, Ps): ︹

PRESENTATION FORM FOR VERTICAL RIGHT TORTOISE SHELL BRACKET (U+FE3A, Pe): ︺

PRESENTATION FORM FOR VERTICAL LEFT BLACK LENTICULAR BRACKET (U+FE3B, Ps): ︻

PRESENTATION FORM FOR VERTICAL RIGHT BLACK LENTICULAR BRACKET (U+FE3C, Pe): ︼

PRESENTATION FORM FOR VERTICAL LEFT DOUBLE ANGLE BRACKET (U+FE3D, Ps): ︽

PRESENTATION FORM FOR VERTICAL RIGHT DOUBLE ANGLE BRACKET (U+FE3E, Pe): ︾

PRESENTATION FORM FOR VERTICAL LEFT ANGLE BRACKET (U+FE3F, Ps): ︿

PRESENTATION FORM FOR VERTICAL RIGHT ANGLE BRACKET (U+FE40, Pe): ﹀

PRESENTATION FORM FOR VERTICAL LEFT CORNER BRACKET (U+FE41, Ps): ﹁

PRESENTATION FORM FOR VERTICAL RIGHT CORNER BRACKET (U+FE42, Pe): ﹂

PRESENTATION FORM FOR VERTICAL LEFT WHITE CORNER BRACKET (U+FE43, Ps): ﹃

PRESENTATION FORM FOR VERTICAL RIGHT WHITE CORNER BRACKET (U+FE44, Pe): ﹄

PRESENTATION FORM FOR VERTICAL LEFT SQUARE BRACKET (U+FE47, Ps): ﹇

PRESENTATION FORM FOR VERTICAL RIGHT SQUARE BRACKET (U+FE48, Pe): ﹈

SMALL LEFT PARENTHESIS (U+FE59, Ps): ﹙

SMALL RIGHT PARENTHESIS (U+FE5A, Pe): ﹚

SMALL LEFT CURLY BRACKET (U+FE5B, Ps): ﹛

SMALL RIGHT CURLY BRACKET (U+FE5C, Pe): ﹜

SMALL LEFT TORTOISE SHELL BRACKET (U+FE5D, Ps): ﹝

SMALL RIGHT TORTOISE SHELL BRACKET (U+FE5E, Pe): ﹞

FULLWIDTH LEFT PARENTHESIS (U+FF08, Ps): （

FULLWIDTH RIGHT PARENTHESIS (U+FF09, Pe): ）

FULLWIDTH LEFT SQUARE BRACKET (U+FF3B, Ps): ［

FULLWIDTH RIGHT SQUARE BRACKET (U+FF3D, Pe): ］

FULLWIDTH LEFT CURLY BRACKET (U+FF5B, Ps): ｛

FULLWIDTH RIGHT CURLY BRACKET (U+FF5D, Pe): ｝

FULLWIDTH LEFT WHITE PARENTHESIS (U+FF5F, Ps): ｟

FULLWIDTH RIGHT WHITE PARENTHESIS (U+FF60, Pe): ｠

HALFWIDTH LEFT CORNER BRACKET (U+FF62, Ps): ｢

HALFWIDTH RIGHT CORNER BRACKET (U+FF63, Pe): ｣

## HTML for the Pause symbol in audio and video control

There are various symbols which could be considered adequate replacements, including:

**| |**- two standard (bolded) vertical bars.▋▋ -

`▋`

and another`▋`

▌▌ -

`▌`

and another`▌`

▍▍ -

`▍`

and another`▍`

▎▎ -

`▎`

and another`▎`

❚❚ -

`❚`

and another`❚`

I may have missed out one or two, but I think these are the better ones. Here's a list of symbols just in case.

## What characters can be used for up/down triangle (arrow without stem) for display in HTML?

Unicode arrows heads:

- ▲ - U+25B2 BLACK UP-POINTING TRIANGLE
- ▼ - U+25BC BLACK DOWN-POINTING TRIANGLE
- ▴ - U+25B4 SMALL BLACK UP-POINTING TRIANGLE
- ▾ - U+25BE SMALL BLACK DOWN-POINTING TRIANGLE

For ▲ and ▼ use `▲`

and `▼`

respectively if you cannot include Unicode characters directly (use UTF-8!).

Note that the font support for the smaller versions is not as good. Better to use the large versions in smaller font.

More Unicode arrows are at:

- http://en.wikipedia.org/wiki/Arrow_%28symbol%29#Arrows_in_Unicode
- http://en.wikipedia.org/wiki/Geometric_Shapes

Lastly, these arrows are not ASCII, including ↑ and ↓: they are Unicode.

## Are there different types of double quotes in utf-8 (PHP, str_replace)?

There are many characters that look like quotation marks, most of them are used infrequently. The ones that are used more often are these three:

`" U+0022 QUOTATION MARK`

“ U+201C LEFT DOUBLE QUOTATION MARK

” U+201D RIGHT DOUBLE QUOTATION MARK

Some rarer ones are FULLWIDTH QUOTATION MARK, the DITTO MARK, the DOUBLE PRIME, the DOUBLE PRIME QUOTATION MARK, and so on. The Unicode.org "confusables" tool finds 15 characters similar to `"`

.

Why don't you copy and paste the offending character here so we can identify it? Or you could use the HEX function to get the hexadecimal encoding of the character, that's another way of identifying it.

## Double quote characters as Octal \223 and \224 on unix sun solaris but the same characters as " html entity on windows. Why?

The `"`

is an ASCII double-quote. Some programs (in particular browsers on Windows) may improve your experience by showing different characters than what was given.

The examples `\223`

and `\224`

are using `cp1252`

, which has been (mis)equated to ISO-8859-1 for the purpose of HTML standardization:

- Anything wrong with using windows-1252 instead of UTF-8
- Single quotes showing as diamond shaped question mark in browsers (no database or PHP)

The actual Unicode values for these are `U+201C`

and `U+201D`

, or as HTMl entities `“`

and `”`

respectively.

You can always use `"`

in a web page of course. But using `\223`

, etc., may not work as expected.

## Python: How can I replace full-width characters with half-width characters?

The built-in `unicodedata`

module can do it:

`>>> import unicodedata`

>>> foo = u'１２３４５６７８９０'

>>> unicodedata.normalize('NFKC', foo)

u'1234567890'

The “NFKC” stands for “Normalization Form KC [Compatibility Decomposition, followed by Canonical Composition]”, and replaces full-width characters by half-width ones, which are Unicode equivalent.

Note that it also normalizes all sorts of other things at the same time, like separate accent marks and Roman numeral symbols.

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