# Symbols for left and right limits

I am using lualatex, are there symbols for left and right limits, like small "-" and "+" to put above the numbers? For now I use

\documentclass[a4paper,12pt]{book}
\usepackage{fontspec}
\usepackage{polyglossia}
\usepackage{amsmath,empheq}
\usepackage{mathtools}
\usepackage{amscd}
\usepackage{amsxtra}
\usepackage{unicode-math}

\begin{document}
$\lim_{x \rightarrow 1^{+}} f(x)$
$\lim_{x \rightarrow 1^{-}} f(x)$
\end{document}


which I feel is not right because the default "+" and "-" are operators and their size and spacing might not be the best for this use.

• Have you considered writing \lim_{x\downarrow1} and \lim_{x\uparrow1}, respectively? That should make pretty clear that right-hand ("from above") and left-hand ("from below") limits are being taken. – Mico May 7 '15 at 11:20
• infix operators like + and - lose their infix status (and the extra space that implies) if used on their own in this way. What you have is the standard markup. – David Carlisle May 7 '15 at 11:27
• Note also that TeX doesn't add spaces around binary operation or relation symbols when used in a superscript or subscript; here the situation is even simpler, as @DavidCarlisle says. – egreg May 7 '15 at 11:36
• @Mico thank you, but I prefer to stick with the convention used by my book. – Emmet May 7 '15 at 17:50
• @egreg and David Carlisle, thank you, I already upvoted your comments, if one of you answer the question I can accept it :) – Emmet May 7 '15 at 17:55

Infix operators like + and - lose their infix status (and the extra space that implies) if used on their own in this way. Also as noted by egreg, in a superscript the operators would get no space even used as an infix operator.