67

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 ]]?

Improve this question
8

4 Answers 4

Reset to default
101

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.

Improve this answer
2
  • 2
    thanks. for double parentheses I prefer the inner line be a curve to some extent like this one i.sstatic.net/bVfPz.png. however \llparenthesis is good. Commented Apr 8, 2013 at 9:51
  • Another option (from Detexify) is \textlbrackdbl and \textrbrackdbl from \usepackage{textcomp}. My markdown editor includes this package but not stmaryrd which is handy! Commented Jul 31, 2021 at 3:14
15

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}

New Computer Modern sample

Improve this answer
1
  • \lParen and \rParen look much nicer than \rrparenthesis and \rrparenthesis! Commented May 13, 2022 at 18:17
10

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}
Improve this answer
2

A version with logix package:

enter image description here

% engine = xelatex/luaLaTeX

\documentclass[12pt]{article}
\usepackage{logix}
\begin{document}
\[
\OpnBrktBar 1 \ClsBrktBar; \OpnParnBar 2 \ClsParnBar; \OpnDblCeil 3 \ClsDblCeil; \OpnDblFloor 4 \ClsDblFloor
\]
\end{document}
Improve this answer

You must log in to answer this question.