Thick Japanese bracket symbols

Question

Is there a way to create this type of thick japanese bracket in the picture far right? I use it to enumerate a puzzle collection like this [number]. Just looking for a way to make it look like in some japanese book typesetting i have seen.

Answer 1

In Unicode the characters are

U+3010 LEFT BLACK LENTICULAR BRACKET 【

U+3011 RIGHT BLACK LENTICULAR BRACKET 】

and are present in the vast majority of OpenType/TrueType fonts supporting Japanese.

Use XeLaTeX or LuaLaTeX and fontspec.

Answer 2

You could design your own using TikZ and the scalerel package.

Two new commands \ljp and \rjp are defined that scale a tikzpicture to the size of a standard parenthesis. The commands take an optional argument that can be \big, \Big, \bigg or \Bigg.

There are three global parameters to adjust the shape however you like: \toplen is the length of the top edge as a percentage of the height. It is set to .25 in the above image. inangle is the angle that the curved portion deviates from vertical. It is set to 30 in the above image. A larger angle will make the symbol thinner. loosen controls the looseness of the curve. Lower value results in less curve.

For example, here is the same image with \toplen set to .35 and \inangle set to 75:

\documentclass{article}

\usepackage{tikz,scalerel}

\newcommand{\toplen}{.25}
\newcommand{\inangle}{30}
\newcommand{\loosen}{1}

\newcommand{\ljp}[1][]{\scalerel*{\tikz{\fill (0,0)--(0,1)--(\toplen,1)to[bend right=\inangle, looseness=\loosen]++(0,-1)--cycle;}}{#1(}}
\newcommand{\rjp}[1][]{\scalerel*{\tikz[xscale=-1]{\fill (0,0)--(0,1)--(\toplen,1)to[bend right=\inangle, looseness=\loosen]++(0,-1)--cycle;}}{#1)}}

\begin{document}

\[
\ljp A+B\rjp(A+B)\quad
\ljp[\Big]\frac{A}{B}\rjp[\Big]\Big(\frac{A}{B}\Big)\quad
\ljp[\bigg]\frac{A}{B}\rjp[\bigg]\bigg(\frac{A}{B}\bigg)
\]

\end{document}