'Floor' and 'ceiling' functions

Question

Is there a convenient way to typeset the floor or ceiling of a number, without needing to separately code the left and right parts? For example, is there some way to do $\ceil{x}$ instead of $\lceil x \rceil$ ?

In case anyone else got here looking for mathjax notation, in mathjax, \lceil and \rceil are the appropriate markups. — Hugh Perkins, Aug 21 '17 at 08:15
For me, $\lceil x \rceil$ was already the solution I was looking for ;) — Christopher K., Aug 29 '19 at 16:24

score 261 · Accepted Answer · answered Jan 25 '12 at 17:15

261

\usepackage{mathtools}
\DeclarePairedDelimiter{\ceil}{\lceil}{\rceil}

The command \ceil will do; if called as \ceil*{x} it will add \left and \right; you can also call it as

\ceil[\big]{x} \ceil[\Big]{x} \ceil[\bigg]{x} \ceil[\Bigg]{x}

to state explicitly the size of the delimiters.

answered Jan 25 '12 at 17:15

egreg

1,121,712

34

Even after more than 10 years of LaTeXing one still learns some new tricks! – yo' Jan 25 '12 at 17:32
25

Don't tell me! I learn new tricks even after 25 years! – egreg Jan 25 '12 at 17:34
@egreg Is there any way to switch the default sizing option, so that \ceil{x} will do what \ceil*{x} would normally do? – jamaicanworm Apr 21 '12 at 17:38
1

@jamaicanworm There is, I believe also on this site. But I won't tell you: use \left and \right only when they are really needed. – egreg Apr 21 '12 at 17:50
2

@jamaicanworm Swap definition of starred and non-starred command discusses switching the starred with non-starred version. – Qrrbrbirlbel Nov 11 '12 at 01:36
12

To typeset the floor function, just replace "ceil" with "floor". This may be obvious, but it might save you the trouble of consulting documentation. – void-pointer Sep 30 '13 at 07:19

Werner · Answer 2 · 2012-01-25T18:32:56.460

24

Here is a simple xparse implementation of \ceil, similar to that provided by mathtools' \DeclarePairedDelimiter:

$xparse implementation of \ceil$

\documentclass{article}
\usepackage{xparse}% http://ctan.org/pkg/xparse
\NewDocumentCommand{\ceil}{s O{} m}{%
  \IfBooleanTF{#1} % starred
    {\left\lceil#3\right\rceil} % \ceil*[..]{..}
    {#2\lceil#3#2\rceil} % \ceil[..]{..}
}
\begin{document}
\[\ceil[\big]{x} \quad \ceil[\Big]{x} \quad \ceil[\bigg]{x} \quad \ceil[\Bigg]{x} \quad \ceil*[\big]{\frac{1}{2}}\]
\end{document}

The optional argument is ignored in the starred version of \ceil*[..]{..}.

edited Jan 25 '12 at 18:32

answered Jan 25 '12 at 17:49

Werner

603,163

4

You could eliminate the \IfNoValueTF {\lceil#3\rceil} if you used {s O{} m}. Then the second arg #2 will be defined so only need #2\lceil#3#2\rceil. – Peter Grill Jan 25 '12 at 18:29

score 2 · Answer 3 · edited Oct 14 '21 at 19:28

2

You can define your command with a simple single line as follow:

\newcommand{\ceil}[1]{\lceil {#1} \rceil}

The above command definition tells that your command takes one input [1] and uses that input between the predefined commands \lceil and \rceil via {#1}

Hope it helps.

edited Oct 14 '21 at 19:28

Imran

3,096

answered Oct 14 '21 at 19:19

eferay

33

Welcome to TeX.SE! – Mensch Oct 14 '21 at 19:30
@Mensch Thanks :) – eferay Oct 14 '21 at 19:39

'Floor' and 'ceiling' functions

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