How to write ceil and floor in latex?

Question

Is there a macro in latex to write ceil(x) and floor(x) in short form? The long form

\left \lceil{x}\right \rceil

is a bit lengthy to type every time it is used.

Welcome to TeX.SX! Your post was migrated here from another Stack Exchange site. Please register on this site, too, and make sure that both accounts are associated with each other (by using the same OpenID), otherwise you won't be able to comment on or accept answers or edit your question. — Joseph Wright, Jun 08 '13 at 05:31
Thank you, it seems I was asking questions in the wrong forum indeed! — danny, Jul 07 '13 at 17:35

score 273 · Accepted Answer · edited Jun 08 '22 at 20:49

273

Using \DeclarePairedDelimiter from mathtools, you could define macros \ceil and \floor, which will scale the delimiters properly (if starred):

\documentclass{minimal}
\usepackage{mathtools}
\DeclarePairedDelimiter\ceil{\lceil}{\rceil}
\DeclarePairedDelimiter\floor{\lfloor}{\rfloor}
\begin{document}
  \begin{equation}
    \floor{\frac{x}{2}} \leq \frac{x}{2} \leq \ceil{\frac{x}{2}}
  \end{equation}
\end{document}

Result:

edited Jun 08 '22 at 20:49

Quantum Guy 123

105

answered Jun 08 '13 at 09:33

You

6,713
2
29
27

4

That's neat. Didn't know about this command. – Jan Jun 08 '13 at 11:47
1

Doesn't work here. Any idea how to do it without mathtools? – David 天宇 Wong Mar 05 '15 at 01:54
3

Just a question: why * when using \floor? I noticed that if the * is omitted from the command, the delimiter does not resize... but why? – Gherardo Jul 11 '15 at 07:26
4

@Gherardo: Check the documentation of the mathtools package. It's just the way the \DeclarePairedDelimiter macro works — you can also make it use a specific size if you want to: \floor[\Bigg]{\frac{x}{2}}. – You Jul 11 '15 at 10:10
40

As a minor side note, the inequality you used as an example is incorrect for all even numbers. – Chris Feb 18 '18 at 13:35
I do not know how the definition works, but \lceil{x}\rceil worked. – puravidaso Jan 19 '21 at 02:09
@Chris I don't see how the inequality is incorrect. – Atom Aug 23 '22 at 14:06
4

@Atom The post was edited after I made this comment. https://tex.stackexchange.com/review/suggested-edits/232037 – Chris Aug 23 '22 at 16:29

score 41 · Answer 2 · edited Apr 13 '17 at 12:35

41

You can define your own macro via the \def command anywhere in your document. For example
```
\def\lc{\left\lceil}   
\def\rc{\right\rceil}
```
and then just write \lc x \rc.
Or you use the \providecommand in the preamble, e.g.
```
\providecommand{\myceil}[1]{\left \lceil #1 \right \rceil }
```
to simply use \myceil{x} in your document.
Use an editor, like vim, that allows for defining shortcuts for quick and efficient editing.
And, finally, don't forget about readability of your tex document. Check out this thread for some instructive comments on how to write efficient and readable tex math docs.

edited Apr 13 '17 at 12:35

Community

1

answered Jun 07 '13 at 20:13

Jan

1,344

4

For 1. In LaTeX you should use \newcommand not \def. For 1. and 2. using \left...\right is not appropriate in a number of situations. – Andrew Swann May 05 '18 at 08:40
How does \providecommand differ from \newcommand? – Paul Wintz Nov 15 '21 at 10:00
1

@PaulWintz If the command already exists, \providecommand will do nothing and \newcommand will cause an error. If the command doesn't exist, they are equivalent. There's also \renewcommand, which will cause an error if the command doesn't already exist. The purpose of the three commands is to make sure you realize when you're overwriting an existing command. – Teepeemm Jun 08 '22 at 20:56

score 22 · Answer 3 · edited May 09 '19 at 21:16

22

This will also work fine without using mathtools.

\newcommand{\floor}[1]{\lfloor #1 \rfloor}

edited May 09 '19 at 21:16

James Mishra

103

answered Jun 24 '15 at 23:29

David Chester

329

6

Welcome to TeX.SX! \floor and \rfloor are amsmath commands, mathtools builds on top of amsmath, so it's no wonder, this would work even without mathtools. The solution with \DeclarePairedDelimiter shows better spacing however. Perhaps you should elaborate on your answer and show some screenshot and a full example, not only fragments of code – Jun 24 '15 at 23:47
2

@ChristianHupfer \lfloor and \rfloor are in core LaTeX. \floor is not defined in amsmath. The \DeclaredPairedDelimiter' is good, but in comparison to the\newcommand` above it mostly provides an easy way to change the code when a different size is required. – Andrew Swann May 05 '18 at 08:44

score 20 · Answer 4 · edited May 05 '18 at 08:52

20

There is no need to use mathtool here:

\newcommand{\floor}[1]{\left\lfloor #1 \right\rfloor}
\newcommand{\ceil}[1]{\left\lceil #1 \right\rceil}

is better than mathtool.

edited May 05 '18 at 08:52

Sebastiano

54,118

answered May 05 '18 at 08:02

latra

95

3

I think this is a comment to one of the previous answers, not an answer... – CarLaTeX May 05 '18 at 08:06
This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review – Bobyandbob May 05 '18 at 08:21
2

@Bobyandbob This most certainly answers the question. It might not be a very good answer (that is certainly my belief), but there should be little doubt that this is an answer to the question asked above. – moewe May 05 '18 at 11:48
1

I strongly disagree with the sentiment that the approach here is better than mathtool. The mathtool approach allows for automatic scaling (which should be used with care, if not avoided at all, because it can give sub-par results in certain cases, see e.g. here - could not find a better example) and manual specification of fence size. – moewe May 05 '18 at 11:52

How to write ceil and floor in latex?

4 Answers4

Linked