# 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 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, 2018 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, 2018 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.
– user45054
Nov 12, 2018 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}. Nov 12, 2018 at 22:18
• I've been nudged. \newcommand{\sparens}[1]{\biggl(\,#1\biggr)} works pretty well.
– user45054
Nov 13, 2018 at 19:14

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