Double square brackets

Question

In many equation editors (e.g. MS Word 2007 and Daum Equation Editor), there's a double square bracket. Is there a TeX equivalent for [[, ((, )), and ]]?

Did you mean the double brackets like in the picture in this question? http://tex.stackexchange.com/questions/48310/what-fonts-are-used-in-this-formula/ — kahen, Apr 06 '13 at 17:36
To the best of my knowledge, there isn't a multiset parenthesis pair in any of the standard fonts. See this question: http://tex.stackexchange.com/questions/5816/multiset-notation-in-latex/ — kahen, Apr 06 '13 at 17:38
For double parentheses see this question: A symbol for the field of formal Laurent series. — Hendrik Vogt, Apr 06 '13 at 18:34
The package stmaryrd seems to have the symbols you're looking for. llparenthesis, llbracket for example. — Sean Allred, Apr 07 '13 at 12:04
@egreg indeed it does :P It was way past my bedtime though ;) — Sean Allred, Apr 08 '13 at 07:11
Link to related questions — ■ ‖ ‖ ■ ‖ ‖ (extensible) ■ ( ‖ ) ■ 〚〛 ■ ⟪ | ⟫ ■ ⟪ ⟫ ■ ⟪ ⟫ without MnSymbol ■ ⟪ ⟫ 〚〛 ⦇ ⦈ ⦃ ⦄ ■ ‖ ⟫ — user202729, Oct 26 '22 at 19:08

Thruston · Accepted Answer · 2021-09-25T15:32:54.980

If you only want then occasionally, perhaps you can just roll-your-own by using a little bit of negative space, like this

Maths in double brackets $[\![ e=mc^2 ]\!]$ or double parentheses $(\!( a^2 )\!)$.

negspace output

Note that they will not scale nicely with \left and \right because of the fixed negative space.

If you'll be using them a lot, try using a package like stmaryrd that defines commands for these symbols, as recommended in the comments.

\documentclass{article}
\usepackage{stmaryrd}
\begin{document}
\begin{equation}
  \llbracket     1 \rrbracket       \quad
  \llparenthesis 2 \rrparenthesis   \quad
  \llceil        3 \rrceil          \quad
  \llfloor       4 \rrfloor         \quad
\end{equation}
\end{document}

stmaryrd output

Note especially the fancier display for double parentheses.

As a side note, DeTeXify is getting better and better at recognizing these symbols, so you can check there for more package-based options.

thanks. for double parentheses I prefer the inner line be a curve to some extent like this one http://i.stack.imgur.com/bVfPz.png. however \llparenthesis is good. — , Apr 08 '13 at 09:51
Another option (from Detexify) is \textlbrackdbl and \textrbrackdbl from \usepackage{textcomp}. My markdown editor includes this package but not stmaryrd which is handy! — Oliver, Jul 31 '21 at 03:14

score 12 · Answer 2 · answered Sep 26 '21 at 15:14

These commands are \lBrack/\rBrack, and either \lParen and \rParen or \llparenthesis and \rrparenthesis in unicode-math or several 8-bit packages, including stix, stix2 and fdsymbol. In Unicode, you can also use the symbols ⟦, ⦅, ⦇, etc.

You might find the \DeclarePairedDelimiter command from mathtools very convenient, especially if you need to specify a size.

\documentclass{article}
\usepackage{mathtools}
\usepackage{newcomputermodern} % Loads unicode-math
\DeclarePairedDelimiter\Brackets{\lBrack}{\rBrack}
\DeclarePairedDelimiter\Parens{\lParen}{\rParen}
\begin{document}
\begin{gather}
   \lBrack x \rBrack \quad \lParen y \rParen \quad
   \llparenthesis z \rrparenthesis \
   \Brackets{u} \quad \Parens{v}
\end{gather}
\end{document}

\lParen and \rParen look much nicer than \rrparenthesis and \rrparenthesis! — Maëlan, May 13 '22 at 18:17

score 5 · Answer 3 · answered Jun 12 '23 at 13:14

In the case that you would have a conflict between stmaryrd and another package, or that you dislike some redefinitions of symbols (such as \bigtriangledown), you may want to use the following line to import only the commands that you wish:

\usepackage[only,llbracket,rrbracket]{stmaryrd}

Double square brackets

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