Unicode for X-double bar

Question

I am looking for the HTML code for the X-double bar.

I know the code for a single bar:

x-bar = x̄ or x̄ (hex)

But what is it for the X-double bar?

Answer 1

The accepted answer is incorrect.

U+035E COMBINING DOUBLE MACRON is meant to go over two code points. It is double only in the sense that it goes over both the code point it follows and the one it precedes, unlike normal marks that only count for the one they follow. Compare U+0360 COMBINING DOUBLE TILDE, which does the same thing. "a\x{35e}e" is a͞e, while "a\x{360}e" is a͠e.

The code point you want is U+033F COMBINING DOUBLE OVERLINE. "x\x{33f}" is x̿.

Here are all the combining macrons, using the uninames tool:

% uninames COMBINING MACRON
  ̄  0304        COMBINING MACRON
        = long
        * distinguish from the following
        x (macron - 00AF)
        x (modifier letter macron - 02C9)
  ̱  0331        COMBINING MACRON BELOW
        x (low line - 005F)
        x (modifier letter low macron - 02CD)
  ͞  035E        COMBINING DOUBLE MACRON
  ͟  035F        COMBINING DOUBLE MACRON BELOW
  ᷄  1DC4       COMBINING MACRON-ACUTE
  ᷅  1DC5       COMBINING GRAVE-MACRON
  ᷆  1DC6       COMBINING MACRON-GRAVE
  ᷇  1DC7       COMBINING ACUTE-MACRON
  ᷋  1DCB       COMBINING BREVE-MACRON
        * Lithuanian dialectology
  ᷌  1DCC       COMBINING MACRON-BREVE
        * Lithuanian dialectology
  ︤  FE24       COMBINING MACRON LEFT HALF
  ︥  FE25       COMBINING MACRON RIGHT HALF
  ︦  FE26       COMBINING CONJOINING MACRON
        x (combining macron - 0304)
        x (combining double macron - 035E)

and here are the combining half marks:

% uninames COMBINING HALF

  ̜  031C        COMBINING LEFT HALF RING BELOW
        * IPA: open variety of vowel
        x (modifier letter down tack - 02D5)
  ̹  0339        COMBINING RIGHT HALF RING BELOW
  ͑  0351        COMBINING LEFT HALF RING ABOVE
  ͗  0357        COMBINING RIGHT HALF RING ABOVE
  ︠  FE20        COMBINING LIGATURE LEFT HALF
  ︡  FE21        COMBINING LIGATURE RIGHT HALF
        x (combining double inverted breve - 0361)
  ︢  FE22        COMBINING DOUBLE TILDE LEFT HALF
  ︣  FE23        COMBINING DOUBLE TILDE RIGHT HALF
        x (combining double tilde - 0360)
  ︤  FE24       COMBINING MACRON LEFT HALF
  ︥  FE25       COMBINING MACRON RIGHT HALF

And these are, well, what they say they are:

% uninames COMBINING DOUBLE LINE
  ̎  030E        COMBINING DOUBLE VERTICAL LINE ABOVE
        * Marshallese
        x (quotation mark - 0022)
  ̳  0333        COMBINING DOUBLE LOW LINE
        = double underline, double underscore
        * connects on left and right
        x (combining equals sign below - 0347)
        x (double low line - 2017)
  ̿  033F        COMBINING DOUBLE OVERLINE
  ͈  0348        COMBINING DOUBLE VERTICAL LINE BELOW
        * IPA: strong articulation

$ uninames '\bAE\b' macron
 Ǣ  01E2        LATIN CAPITAL LETTER AE WITH MACRON
        : 00C6 0304
 ǣ  01E3        LATIN SMALL LETTER AE WITH MACRON
        * Old Norse, Old English
        : 00E6 0304

You can test them this out way:

$ export PERL_UNICODE=S

$ perl -E 'say "x\x{33f}"'
x̿

$ perl -E 'say "a\x{35e}e"'
a͞e
$ perl -E 'say "a\x{360}e"'
a͠e
$ perl -E 'say "a\x{fe24}e\x{fe25}"'
a︤e︥

$ perl -E 'say "\x{1e3}"'
ǣ
$ perl -E 'say "\x{e6}\x{304}"'
ǣ
$ perl -E 'say "\x{e6}\x{33f}"'
æ̿

$ perl -E 'say "X\x{304}"'
X̄
$ perl -E 'say "X\x{33f}"'
X̿
$ perl -E 'say "x\x{33f}\x{333}"'
x̳̿

Answer 2

For whichever character you want to put bars above, add ̄ after it.

So for example if you want x double bar (x̄̄) the HTML code is x̄̄. If you want to make an x triple bar (x̄̄̄) then write x̄̄̄.

Here's a code sample in HTML:

X single bar: x&#772;<br>
X double bar: x&#772;&#772;<br>
X triple bar: x&#772;&#772;&#772;<br>

This also works for any character. For example, for y triple bar (ȳ̄̄), it will be ȳ̄̄.