# Spacing *inside* \left and \right

The simple formula

$\left(\sum_{k=0}^\infty a_k\right)$

produces an irksome, asymmetrical hiccup. The left paren is just a hair too close to the subscript of the summation and the right paren is 1.5 hairs too far to the right of the sum's term. It would be nice if I could literally just nudge the entire summation to the right a little bit, without moving the parentheses, each time I find myself in this situation. The ideal seems to be

\left(\mspace{1.5mu}\sum_{k=0}^\infty a_k\!\right) %requires amsmath

I really only have this problem with series; for example, integrals are fine with the default spacings because the slanted integral necessitates some whitespace:

\left(\int_a^b f(x)\mathrm{d}x\right) %perfectly fine

I thought someone would have surely asked about this already, but I haven't been able to find it (redirect me if this already exists).

I am also implementing a solution to a separate problem of spacing around \left and \right found here: Spacing around \left and \right that I would like this to be compatible with.

• A first mistake is to employ \left and \right to auto-size the round parentheses. If you used the typographically appropriate \biggl and \biggr sizing macros, or maybe even \Bigl and \Bigr, the left-hand-side spacing issue you’ve identified wouldn’t be an issue, and the right-hand-side spacing issue would be much less severe (or even a non-issue). – Mico Nov 12 '18 at 21:11
• For more information on why it's sometimes (or, rather, quite often) not a good idea to auto-size mathematical "fences" via \left and \right, see the posting Is it ever bad to use \left and \right? – Mico Nov 12 '18 at 21:17
• @Mico the use of \bigl, \biggl, and the right versions looks a little odd to me. The textbooks that I have on hand have clearly used something more akin to \left and \right or have avoided the construction altogether. But it is good information. However, even using those TexBook preferred methods in the answers in your link invoke the use of manual spacing. Just so that this doesn't delve into typographical taste though, I'm still looking for a parenthetical construction of series that doesn't use manual spacing repeatedly and avoids those spacing issues I've mentioned. – Robert Wolfe Nov 12 '18 at 21:29
• When I have a summation with wide limits above or below, I add \, before \sum. This is not required and, in my opinion it's worse, with \Bigl(\sum_{k}.... I never use \left and \right around big operators, the resulting size is always too big. I don't think that \mspace{1.5mu} is sufficient in the above case; \, is the same as \mspace{3mu}. – egreg Nov 12 '18 at 22:18
• I've been nudged. \newcommand{\sparens}[1]{\biggl(\,#1\biggr)} works pretty well. – Robert Wolfe Nov 13 '18 at 19:14

Following the comments, \newcommand{\sparens}[1]{\biggl(\,#1\biggr)} works pretty well.