# How to make a matrix with \llfloor and \rrfloor and how to make smaller distance between two curly brackets?

I am working on brackets.

1) I want to make a smaller distance between curly brackets like this $\{\!\!\{A, B\}\!\!\}$ in equation

$$\left\{\left\{\begin{array}{l} A \\ B \end{array}\right\}\right\}$$.

I am using package stmaryrd.

How can I do this?

2) Also, I would like to make matrices with brackets llfloor, rrfloor and llceil, rrceil:

$\left\llfloor \begin{matrix} A \\ B \end{matrix} \right\rrfloor$ and

$\left\llceil \begin{matrix} A \\ B \end{matrix} \right\rrceil$,

but the problem is that both brackets are smaller than A and B in column.

With non-double floor and ceiling, it is in the same lenght:

Here is the full document:


\documentclass{article}

\usepackage{amssymb}

\usepackage{amsmath}

\usepackage{amsthm}

\usepackage{amsfonts}

\usepackage{amscd}

\usepackage{stmaryrd}

\newcommand{\bbrack}[1]{
\left\llbracket \begin{matrix} #1 \end{matrix} \right\rrbracket}
\newenvironment{bbsmallmatrix}{
\left\llbracket\begin{smallmatrix}}{
\end{smallmatrix}\right\rrbracket}

\begin{document}

$$\bbrack{ A\\ B}$$
$$\left.\llfloor \begin{matrix} A \\ B \\ \end{matrix} \right.\rrfloor$$
$$\left\lfloor \begin{matrix} A \\ B \\ \end{matrix} \right\rfloor$$

$$\left\{\left\{\begin{array}{l} A \\ B \end{array}\right\}\right\}$$

\end{document}


What can I do?

Thanks a lot.

• please provide an example that reproduces the error, not disconnected fragments. You can only use a command with \left if it is declared as a character defined as extensible in the font. so it depends how you have defined \llfloor Aug 26, 2023 at 16:01
• I have managed to fix the error problem by putting . before \llceil or \rrceil. But LaTeX still generates the brackets smaller than A and B (I have added a print screen to my question). Aug 26, 2023 at 16:40
• putting . is same as removing \left (but with worse spacing) Aug 26, 2023 at 16:41
• you still have not provided a test document, I don't know of any font with an extendable character |⌊ Aug 26, 2023 at 16:44
• Thank you. I am glad that the error porblem is fixed. Do you know what to do to make floor and ceil on both sides the same lenght as A and B in column? With non-dobule floor and ceil it is the same lenght (I have also added a picture to compare). Thanks a lot. Aug 26, 2023 at 16:48

\documentclass{article}
$\left\lfloor\!\!\!\left\lfloor\! \begin{matrix} 1\\2\\3 \end{matrix} \!\right\rfloor\!\!\!\right\rfloor$
`