Matrix in double-struck square bracket style

Question

We can use \llbracket \rrbracket using the \usepackage{stmaryrd} to generate double bracket. My question is:

how we can generate a matrix with double bracket (in the same style as the \llbracket \rrbracket version)?

Edit: I just come up with the following way to make a vector form with two dimension:

\providecommand{\matbrack}[2]{
\left\llbracket
\begin{matrix}
    #1 \\
    #2
\end{matrix}
\right\rrbracket
}

Inside text:

$\vecbrack{M}{1}$

score 8 · Accepted Answer · answered Jul 14 '20 at 05:40

I suggest generalizing the command you have in mind by making it take just 1 argument. That way, it can be used for scalars, column and row vectors of arbitrary length, and entire matrices. I would also like to suggest creating a variant of the smallmatrix environment (provided by the amsmath package) that's surrounded by double-struck brackets, for use in inline math settings.

\documentclass{article}
\usepackage{amsmath}  % for 'matrix' env.
\usepackage{stmaryrd} % for '\llbracket' and '\rrbracket'
\newcommand{\bbrack}[1]{%
    \left\llbracket \begin{matrix} #1 \end{matrix} \right\rrbracket}
% for use in inline math:
\newenvironment{bbsmallmatrix}{% 
    \left\llbracket\begin{smallmatrix}}{%
    \end{smallmatrix}\right\rrbracket}
\begin{document}
aaa $\bbrack{ M \ 1 }$ zzz
\quad
aaa $\begin{bbsmallmatrix} M \ 1 \end{bbsmallmatrix}$ zzz
\end{document}

Dear @Mico: Excellent. Especially the ``bbsmallmatrix". :) – Amin Jul 14 '20 at 06:50 — Amin, Jul 14 '20 at 06:50

Davislor · Answer 2 · 2020-12-11T21:54:49.980

4

These brackets are \lBrack and \rBrack in unicode-math, stix or stix2. A simple example of use:

\documentclass{article}
\usepackage{mathtools}
\usepackage{unicode-math}
\DeclarePairedDelimiter{\Brack}{\lBrack}{\rBrack}
\newenvironment{bbmatrix}%
  {\left\lBrack\begin{matrix}}%
  {\end{matrix}\right\rBrack}
\begin{document}
[ \Brack{ \rho, \vartheta, \varphi } 
   \begin{bbmatrix}
   a &b &c \
   d &e &f \
  \alpha & \beta & \gamma
   \end{bbmatrix}
]
\end{document}

edited Dec 11 '20 at 21:54

answered Nov 29 '20 at 05:14

Davislor

44,045

Good answer, but the unicode-math package give some problems to me. SO I've combined with @Mico's anwer and use stmaryrd package and commands \rrbracket and \llbracket instead of \lBrack and \rBrack – Tito Eliatron Dec 11 '20 at 09:22

score 2 · Answer 3 · answered Nov 29 '20 at 03:13

Expanding on Mico's answer above, if you do NOT want to use the stmaryrd package, you can define a new command:

\newcommand{\bbrack}[1]{{
  \mathchoice
    {\left\lbrack\!\!\left\lbrack #1 \right\rbrack\!\!\right\rbrack} % display style
    {\left\lbrack\!\left\lbrack #1 \right\rbrack\!\right\rbrack} % text style
    {} % script style
    {} % scriptscript style
  }
}

to handle arbitrary length scalars, vectors, and matrices. This has the added benefit of looking like \llbracket and \rrbracket.

\documentclass{article}
\usepackage{amsmath}
\newcommand{\bbrack}[1]{{
  \mathchoice
    {\left\lbrack!!\left\lbrack #1 \right\rbrack!!\right\rbrack} % display style
    {\left\lbrack!\left\lbrack #1 \right\rbrack!\right\rbrack} % text style
    {} % script style
    {} % scriptscript style
  }
}
\begin{document}
Inline style: $\bbrack{\mathcal{K}, \mathcal{M}}$
With inline small matrix: $\bbrack{ \begin{smallmatrix} M \ 1 \end{smallmatrix}}$
Finally, normal display style would look like,
\begin{equation}
\bbrack{
  \begin{matrix} 
    0 & D & 0 & 0 & M & 0 & 0 & 0\
    M & 0 & 0 & 0 & M & 0 & 0 & 0 \
    0 & 0 & 1 & 0 & M & 0 & 0 & 0\
    0 & 0 & 1 & 0 & M & 0 & 0 & 0\
    0 & 0 & 1 & 0 & M & 0 & 0 & 0\
    0 & 0 & 1 & \varphi & M & 0 & 0 & 0\
    0 & 0 & 1 & 0 & M & 0 & \ddots & \vdots \
    0 & 0 & 1 & 0 & M & 0 & \dots & 0\
  \end{matrix}
}
\end{equation}
\end{document}

Matrix in double-struck square bracket style

3 Answers3

Linked