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I need some doubled versions of the standard parentheses, namely parentheses, braces, brackets and angles. They should be scalable and the output should look roughly like this:

\documentclass[border=3mm, varwidth]{standalone}
\usepackage{mathtools}

\begin{document}

$\left\lbrack\!\left\lbrack a\right\rbrack\!\right\rbrack$
$\left\lbrack\!\!\left\lbrack \frac12\right\rbrack\!\!\right\rbrack$
$\left\lbrack\!\!\left\lbrack \dfrac{1}{2}\right\rbrack\!\!\right\rbrack$

$\left\lbrace\!\!\left\lbrace a\right\rbrace\!\!\right\rbrace$
$\left\lbrace\!\!\left\lbrace \frac12\right\rbrace\!\!\right\rbrace$
$\left\lbrace\!\!\!\left\lbrace \dfrac{1}{2}\right\rbrace\!\!\!\right\rbrace$

\end{document}

For example, the package stmaryrd provides the commands \llbracket resp. \rrbracket for doubled brackets. However I have some compatability issues with this package and also, the other delimiters are missing. Finally, I would like to be able to turn my symbols into Delimiters using the mathtools functionality. How can I achieve all this?

Edit: Bernard found a package providing doubled brackets and doubled angles (thanks for this!) but I am still interested in the other symbols.

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    Welcome to TeX SX! mathabx provides\ldbracket (alias \semantic)and \rdbracket (\rsemantic). MnSymbol has \lsem, \rsem, \llangle, rrangle. – Bernard Jan 28 '18 at 14:30
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    the stmaryrd package might help. Also, this is related: https://tex.stackexchange.com/questions/100966/defining-scalable-white-curly-brackets-and-and – Steven B. Segletes Jan 29 '18 at 11:04
  • If you are prepared to use lua or xe latex, then unicode math provides most of these depending the font chosen. See unimath-symbols at http://mirrors.dotsrc.org/ctan/macros/latex/contrib/unicode-math/unimath-symbols.pdf for the coverage. – Andrew Swann Jan 29 '18 at 11:11
  • @andrewswann actually I did not know a thing such as lua latex existed. I tried it out now and whilst breaking some parts of my document, the usage of unimath-symbols basically works. However the commands \lBrace and \rBrace don't work and neither does the scaling of e.g. \lAngle and \rAngle using \big or \left. Any Ideas what I am doing wrong? –  Jan 29 '18 at 11:38
  • Pure guess, you have written something like \setmathfont{xits} instead of \setmathfont{xits math}. Otherwise please edit your question to show the code you have tried. – Andrew Swann Jan 29 '18 at 12:04
  • If the answer below fits your needs, consider to upvote and accept it please in order to show your appreciation of Andrew Swann's work done to help you. –  Feb 28 '18 at 09:33
  • Duplicate of [] and () • {} (pdflatex only, no Unicode) • <>. Unrelated, but there's also || – user202729 Dec 17 '21 at 05:42

1 Answers1

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If you are prepared to use lualatex or xelatex then you can use unicode-math. Several of the fonts there provide the brackets you ask for including the XITS font.

Sample output

% arara: lualatex
\documentclass{article}
\usepackage{unicode-math,mathtools}
\setmainfont{xits}
\setmathfont{xits math}

\begin{document}

$\left\lBrack a \right\rBrack$
$\left\lBrack \frac12 \right\rBrack$
$\left\lBrack \dfrac{1}{2}\right\rBrack$

$\left\lBrace a \right\rBrace$
$\left\lBrace \frac12 \right\rBrace$
$\left\lBrace \dfrac{1}{2} \right\rBrace$

$\left\lParen a \right\rParen$
$\left\lParen \frac12 \right\rParen$
$\left\lParen \dfrac{1}{2} \right\rParen$

$\left\lAngle a \right\rAngle$
$\left\lAngle \frac12 \right\rAngle$
$\left\lAngle \dfrac{1}{2} \right\rAngle$

\end{document}
Andrew Swann
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