[Tex/LaTex] \limits and \biggl\lparen

Question

When I type \biggl\lparen before \int\limits, where \limits puts the domain over which I'm integrating under the integral sign, the bottom end of the left parenthesis touch — or is too close to — the domain symbol ; and it causes poor readability.

Here is an example :

\biggl\lparen \int\limits_{\{\lvert x \rvert > R \}} u(x) dx \biggr\rparen

I have overcome this difficulty by adding a space after the left parenthesis with \>. More precisely, I defined the following PairedDelimiter :

\DeclarePairedDelimiterX{\parens}[1]{\lparen}{\rparen}{\> #1}

However, I am not satisfied by this « solution » because I do not need the extra spacing all the time, and that makes \parens not flexible at all.

I don't want to use \left and \right, since they make the parentheses too big ; nor \Bigl and \Bigr which make the parentheses too small.

I'm open to any suggestion.

Thanks !

Answer 1

Since it looks like you're using the mathtools package (good move!), I suggest you do the following:

• use the \smashoperator[r]{...} directive (provided by the mathtools package) to eliminate the whitespace between the integral symbol and the integrand;

• define a new macro called \abs using \DeclarePairedDelimiter;

• define the macro \parens using \DeclarePairedDelimiter as well, and use \parens[\bigg]{...} to generate the bigg-sized parentheses;

• insert a thinspace between the integrand and dx; optional: write \mathrm{d}x if you want the "differential operator" set in upright rather than in italic mode;

• add a bit of whitespace after \biggl\lparen to separate visually the large opening parenthesis from the domain of integration (\,\, seems about right to me, but your preferences may differ); and

• omit the curly braces around the expression for the domain of integration.

\documentclass{article}
\usepackage{mathtools}
\DeclarePairedDelimiter{\abs}{\lvert}{\rvert}
\DeclarePairedDelimiter{\parens}{\lparen}{\rparen}
\begin{document}
\begin{align*}
\texttt{before:}&\quad
\biggl\lparen \int\limits_{\{\lvert x \rvert > R \}} u(x) dx \biggr\rparen\\[2ex]
\texttt{after:}&\quad
\parens[\bigg]{\,\, \smashoperator[r]{\int\limits_{\abs{x}> R }} u(x) \, dx }
\end{align*}
\end{document} 

---

Addendum: In a follow-up comment, the OP mentioned that he/she uses the mathptmx package, and that \bigg-sized parentheses turn out to be too big and that \Big-sized parentheses are not big enough. I suggest looking into using the MathTime Professional II font package, which provides high-quality math fonts based on Times Roman. (The complete mtpro2 package isn't free of charge. However, its "lite" subset, which is all that's needed for the present example, is free of charge.)

\documentclass{article}
\usepackage{newtxtext}    % Times Roman text font
\usepackage[lite]{mtpro2} % Times Roman math font
\usepackage{mathtools}
\DeclarePairedDelimiter{\abs}{\lvert}{\rvert}
\DeclarePairedDelimiter{\parens}{\lparen}{\rparen}
\begin{document}
\[
\parens[\bigg]{\mkern6mu \smashoperator[r]{\int\limits_{\abs{x}> R }} \! u(x) \, dx }
\]
\end{document} 

One may also give the newtxmath package (load it with the option cmintegrals) a try. In my opinion, though, the large parentheses produced by newtxmath look rather anemic; they're certainly not as handsome as those that are produced by the mtpro2 package. Moreover, it's necessary to use \Bigg as the sizing directive the parentheses.

(Same code as in the preceding MWE, with \usepackage[lite]{mtpro2} replaced with \usepackage[cmintegrals]{newtxmath}, and with \Bigg instead of \bigg as the sizing instruction.)