Universal Parentheses

Question

I know it's a bit of an odd request but it is one to which the solution would save me a lot of time.

I write a lot of documents in LaTex (especially maths - no surprise) and I prefer the look of

$\left(\right)$

parentheses on a lot of things because they actually encompass the things inside. For example:

$\deg\left(m_{\alpha_{1}/K}\right)$

looks better than

$\deg(m_{\alpha_{1}/K})$

in my opinion.

Unfortunately, writing \left and \right every time is a bit tiresome.

Is there any way that I can make them all do it automatically? There is a solution here: automatic size adjustment for nested parentheses but it interferes with tikz (presumably because it affects the parentheses).

I tried a solution like

$\newcommand{\(}{\left(}$

but LaTeX didn't like that.

Answer 1

Making ( active is not really a solution because it is used in so many other ways, but here is how it would be done.

To help in this regard. I create \pactive to make ( active which, if used inside a group like an equation, can revert ( to its normal definition after the group is closed.

\documentclass{article}
\let\svlp(
\catcode`(=\active %
\def(#1){\left\svlp#1\right)}
\catcode`(=12 %
\newcommand\pactive{\catcode`(=\active }
\begin{document}
\[
\pactive
\deg(m_{\alpha_{1}/K}) + (\frac{a}{x+c})
\]
Normal use of ( or even \fbox{\makebox(20,30){test}}
\end{document}

The OP asks about automating the invocation of \pactive. Again, I don't recommend it, because there may be need in math mode to use the () set as an argument to some macro. But the use of

\everymath{\pactive}
\everydisplay{\pactive}

will accomplish it:

\documentclass{article}
\let\svlp(
\catcode`(=\active %
\def(#1){\left\svlp#1\right)}
\catcode`(=12 %
\newcommand\pactive{\catcode`(=\active }
\everymath{\pactive}
\everydisplay{\pactive}
\begin{document}
\[
%\pactive
\deg(m_{\alpha_{1}/K}) + (\frac{a}{x+c})
\]
Normal use of ( or even \fbox{\makebox(20,30){test}}

\(
%\pactive
\deg(m_{\alpha_{1}/K}) + (\frac{a}{x+c})
\)
Normal use of ( or even \fbox{\makebox(20,30){test}}
\end{document}

Thanks to Timm for reminding that, if one really wants to automate this, then one should have handy the override macro

\newcommand\pinactive{\catcode`(=12 }

Answer 2

An easy solution would just be to use the qty command from the physics package. Here's a MWE:

\documentclass{article}
\usepackage{physics}
\begin{document}
With \texttt{qty}:
\[
\qty(m_{\frac\alpha\beta}) + \qty(\frac{1}{x+y}) + \qty(\int^{\infty}_{0} x^2 \dd{x})
\]

Without \texttt{qty}:
\[
(m_{\frac\alpha\beta}) + (\frac{1}{x+y}) + (\int^{\infty}_{0} x^2 \dd{x})
\]
\end{document}

Answer 3

It's definitely a bad idea, but if you really want to get ugly documents, here it is. ;-)

\documentclass{article}

\newcommand{\extlparen}{\left\delimiter"4028300 }
\newcommand{\extrparen}{\right\delimiter"5029301 }
\begingroup\lccode`~=`( \lowercase{\endgroup\let~}\extlparen
\begingroup\lccode`~=`) \lowercase{\endgroup\let~}\extrparen

\AtBeginDocument{\mathcode`(="8000 \mathcode`)="8000 }

\begin{document}
\[
\deg(m_{\alpha_{1}/K})+(\sum_{i=1}^n i^2)
\]
\end{document}

The same with proper markup:

\[
\deg(m_{\alpha_{1}/K})+\biggl(\,\sum_{i=1}^n i^2\biggr)
\]

The parentheses are much better in the second case than in the top one.

Answer 4

While you ask about an automatic solution to this, i would still like to present a systematic Approach to this. The mathtools package allows you to define commands with paired delimiters. The starred variants of the command (the one you created) adds a \left and a \right:

\documentclass{article}

\usepackage{mathtools}
% 'braced' fraction:
\DeclarePairedDelimiterX\bfrac[2]{(}{)}{\frac{#1}{#2}}

\begin{document}
    \begin{align*}
        \bfrac{a}{x + c} + \bfrac*{a}{x + c}
    \end{align*}
\end{document}

Sorry, i can't post a screenshot now, but the first fraction puts normal braces, the second one bigger ones (scaled with \left and \right).

Note that the starred Version of \bfrac was not defined.

One can do a lot of stuff with this, i recommend reading the respective part in the mathtools manual.

Answer 5

I think the mathtools package gives the perfect solution to the original problem. You put

\DeclarePairedDelimiter\paren{\lparen}{\rparen}

\paren*{\frac12}

The starred version allows the parentheses grow automatically. If you do not like how the parenthesis grows, you can specify the exact size

\paren[\Big]{\frac12}

Here is a full example

\documentclass{article}

\usepackage{mathtools}
\DeclarePairedDelimiter{\paren}{\lparen}{\rparen}

\begin{document}
Here with the starred version of the command, the parentheses grow
automatically, the nonstarred just gives the usual parens, and in the
third version with the 'Big' option, you specify the size by hand.  

\begin{equation*}
  \paren*{\frac12} \quad \paren{\frac12} \quad \paren[\Big]{\frac12} 
\end{equation*}
\end{document}

You can see the output at http://wd369.csi.hu/apu/paren.png

Answer 6

Using plain TeX commands inside a LaTeX document, this is pretty straightforward:

\documentclass{article}

\let\lparen(
\let\rparen)
\catcode`(=\active
\catcode`)=\active
\def({\ifmmode\left\fi\lparen}
\def){\ifmmode\right\fi\rparen}

\begin{document}

\[
  \deg(m_{\alpha_{1}/K})+(\sum_{i=1}^n i^2)
\]

In the rare case that you need normal parentheses:

\[
  \deg\lparen m_{\alpha_{1}/K}\rparen+\lparen\sum_{i=1}^n i^2\rparen
\]

This is (pretty) normal text.

\end{document}

It's just making \lparen an alias for an ordinary parenthesis and then redefining it. After that, you can still use the \lparen macro, just in case you don't like the active parentheses.

Answer 7

Another option is to use the nath package:

\documentclass{article}
\usepackage{nath}
\begin{document}
\(
\deg(\frac{m_{\alpha_{1}}}{K}) + (\sum_{i=1}^n i^2)
\)
\[
\deg(\frac{m_{\alpha_{1}}}{K}) + (\sum_{i=1}^n i^2)
\]
\end{document}

which gives:

Note that the scaling of delimiters is better than the default scaling with \left( ... \right). As an added bonus, \frac behaves intelligently in inline vs display mode.

Answer 8

I often use the xparse package to define operators that can take parenthesized input, but if they don't find that input, they treat themselves as not having any input.

\documentclass{article}
\usepackage{mathtools}
\usepackage{xparse}
\RenewDocumentCommand\deg{d()}{\ensuremath{\operatorname{deg}\IfValueT{#1}{\left(#1\right)}}}
\begin{document}
The degree \(\deg\) of the vector bundle \(V\) is 
\[
\deg(V) = 1.
\]
Its slope is \(\deg/\operatorname{rank}\).
\end{document}

Answer 9

Something that I use is the following:

\newcommand\del[1]{\left( #1 \right)}
\newcommand\sbr[1]{\left[ #1 \right]}
\newcommand\cbr[1]{\left\{ #1 \right\}}
\newcommand\abr[1]{\left\langle #1 \right\rangle}

Then in the code, one can just use \del{ ... } and get delimiters. Also I can just change del to sbr if I want to have square brackets.

The package commath also defines very similar commands, but that package has very mixed reviews.

Answer 10

I personally use the vim-latex suite. It makes your life easier in many ways, and on of them is the automatic replacement for brackets, underscores and circumflexes if typed doubled, so that (( becomes \left( \right)<++>, as well as for example __ becomes _{}<++>.

So it's always you who decides if to use the scaled version, but if you want it, it's only a second opening bracket away.

Answer 11

May not be the best solution at all but you can try editing your document with TexStudio. It is a LaTeX editor which has a special tab to insert delimiters and other practical things in your document.

Answer 12

This was stated above but I really like using the physics package, specifically the \qty command for auto-sized parentheses, braces, brackets, etc. the only issue is how that command adds spacing that can look quite bad when you pair \qty with any function. for example: \sin \qty(x). An easy workaround to this unpleasant consequence of the \qty command is just adding a negative space from: \!. To make my example from above \sin \! \qty(x), I find this to be easier than the \left(\right)since that also produces the same unwanted space that \qty makes. There are many more details on how to use the physics package here: http://mirrors.ibiblio.org/CTAN/macros/latex/contrib/physics/physics.pdf. thanks for reading my response!