Latex Math Mode – Rounding to Nearest Integer Symbol in Latex

Question

There are some threads here, in which it is explained how to use \lceil \rceil \lfloor \rfloor.

But generally, in math, there is a sign that looks like a combination of ceil and floor, which means round, aka nearest integer.

Is there a way to draw this sign in Latex's math mode?

Answer 1

The mathtools package has a \DeclarePairedDelimiter command which lets you define such macros. I defined a \nint command which encloses its argument between \lfloor and \rceil. The starred version adds a pair of implicit \left...\right, but you may fine-tune the delimiters size using one of \big, \Big, \bigg, \Biggas an optional argument.

\documentclass[10pt,a4paper]{article}
\usepackage{mathtools, nccmath}

\DeclarePairedDelimiter{\nint}\lfloor\rceil

\DeclarePairedDelimiter{\abs}\lvert\rvert

\begin{document}

    \[ \nint{x}\qquad \nint*{\sqrt{x^2 + \mfrac13}}\qquad\nint[\Big]{\sqrt{x^2}} = \abs{x}\]%

\end{document}