Are \( and \) preferable to dollar signs for math mode?

Question

Along the lines of Why is \[ ... \] preferable to $$ ... $$?, what reasons are there (if any) to favor \( ... \) over $ ... $?

Answer 1

\( ... \) is LaTeX syntax. $ ... $ is TeX syntax.

plainTeX only allows $. In LaTeX you can use both, but \( ... \) will give less obscure error messages when there is a mistake inside it.

Both are shortcuts to start inline math environments.

Answer 2

Anyone who's ever tried writing a simple perl (or whatever) script to quickly parse a LaTeX document and do something in maths mode but not in text mode will agree that \( .. \) is the only way to go! Trying to get the pattern matching right against $a^2 + b^2$$c^2 + d^2$ is a nightmare.

(Before anyone asks, yes I have, and it's called mathgrep. The pain and agony of writing that convinced me more than anything else of the value of making everything a configurable macro so it can be easily changed later.)

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Another reason: looking at the code, \( and \) actually checks that TeX is in the right mode before starting. So hello \(world \(can\) we\) have some tea? will produce an error, whereas hello $world $can$ we$ have some tea? will not.

Answer 3

Interestingly, nobody mentioned that the mathtools package has a very nice feature of adding italic correction in some places at the boundary between text and math mode (see its documentation for details, but aesthetically this really matters!), and this feature works only with \(...\).

The first line is with correction, the second without.

Answer 4

It is instructive to examine the exact definitions of \( and \) that are provided by the LaTeX kernel (contained in the file latex.ltx), version early 2016:

\DeclareRobustCommand\({%
  \relax\ifmmode\@badmath\else$\fi}%
\DeclareRobustCommand\){%
  \relax\ifmmode\ifinner$\else\@badmath\fi\else\@badmath\fi}%

The main thing to note is that \( and \) act as "wrappers" around the "$" token:

• \( checks first if it occurs in ("inner" or "outer") math mode. If that's the case, it issues an error message, viz., "LaTeX Error: Bad math environment delimiter", as it can't be correct to initiate inline math mode if TeX is already in math mode. If it's not the case, i.e. if \( is encountered while TeX is not in math mode, a single $ token is inserted and TeX's inline math mode is thereby entered.

• Likewise, \) checks first if it occurs in "inner" math mode. If that's not the case, i.e., if TeX is either in "outer" math mode or not in math mode at all, a "LaTeX Error: Bad math environment delimiter" error message is generated. If, on the other hand, TeX is in inner math mode, a single $ token is generated and inline math mode is thereby terminated.

Moreover, observe that both \( and \) are declared to be "robust". This means, inter alia, that both macros can be used inside "moving" arguments, e.g., inside the arguments of sectioning commands and \captions. (Aside: Robustness of these two macros was not the default in versions of the LaTeX kernel prior to 2015, necessitating the loading of the fixltx2e package -- which is something, I think is fair to say, few people ever did...)

Do these observations imply that using \( ... \) is preferable to typing $ ... $? Not necessarily! First, the LaTeX error message one gets from typing (say) \[a\) -- "! LaTeX Error: Bad math environment delimiter." -- is not necessarily more informative or helpful than the TeX error message that results from typing \[a$ -- "! Display math should end with $$." Second, if your inline math expressions contain a lot of opening and closing round parentheses, i.e., ( and ), the presence of \( and \) can be quite distracting if one needs to debug an inline equation and locate where an opening or closing parenthesis may be missing.

Separately, depending on the exact layout of your keyboard, typing \( and \) may also entail (marginally) more effort than typing $ does. Of course, the input effort will also depend importantly on the editor that's being used.

Answer 5

There are some good 'meta' reasons for using \( ... \) in some circumstances. Environments such as Fancy Verbatim and alltt will allow \( and \) to act as math mode, but $ will be interpreted as a literal.

Another convenience is that some editors have an easier time with pair matching \( ... \) than $.

Answer 6

There is actually a very good reason to prefer \( ... \) over $ ... $, but it's relevant only in one specific context I can think of: If you have a macro that applies an argument like this $#1$, supplying an empty argument when using the macro (which might make, depending on the command, perfect sense) would lead to an obscure error message, whereas \(#1\) will not.

An update (thanks to a comment by @BrunoLeFloch): As the above problem can be circumvented by writing $ #1$ instead, a better way of thinking about this is the following: It is better to teach people \( ... \) than $ ... $, though technically the disadvantages of using the latter are minor and can be circumvented with enough knowledge. Teaching people the former means that they need to pay attention to at least one fewer trap caused by the fact that TeX practically treats both $ and $$ as tokens.

Answer 7

Configuring \( and \) for inline math tags in MathJax is beneficial as you don't need to escape $ in your HTML contents.

Note: MathJax is a javascript library to render LaTeX commands on the browser.

Answer 8

For users of the package soul:

The soul manual states that its macros* accept math mode within their arguments, but only if $...$ is used; i.e. \(...\) interestingly doesn't work there.

*The manual's example is \so{foo$x^3$bar}, which uses the spacing-out macro \so, and I've tested it with the strikeout macro \st.

Answer 9

Here's a new answer to an old post, in which I'd like to offer the opposite view (and then duck below the parapet): I prefer $...$ and will continue to use it; furthermore, I will teach the use of both $...$ and \(...\) so individuals can make up their own mind. Various points below have been mentioned in comments on other answers, but no answer has yet overtly flown the flag for $...$. Here, I will do that.

The most important thing is this: you're not a bad person if you use $...$. Each to their own!

So, here are my reasons for preferring $...$ over \(...\):

• Typing \( involves two keystrokes, whereas $ involves just one. In a typical math-rich document (e.g. mathematical research articles or teaching material), you'll find that most sentences switch in and out of math mode at least once, and typically several times. A (relatively short) paper I'm working on currently contains 1,286 $ symbols (i.e. 643 pieces of inline maths).
• LaTeX source is harder to read when you use \(...\). As Mico points out in their answer (https://tex.stackexchange.com/a/305471/96966), this becomes especially problematic when the maths also contains parentheses.
• While \(...\) has better error reporting, you commit fewer errors with $...$. Furthermore, errors you commit are easier to spot. This follows as a result of both of the reasons above (number of keystrokes and readability of LaTeX source).
• If \(...\) is ever needed (e.g. for search/replace), it's easy to switch. Your correctly-compiling LaTeX document will contain an even number of $ signs. You can systematically replace each occurrence of $...$ with \(...\) via regular expressions (and vice-versa).

Answer 10

While no one has mentioned it, it's best to use \( ... \), that is because ChkTeX for automated linting recommends using it over $ ... $, which is a good indicator probably.

Answer 11

Here are some mitigating factors for the disadvantages of \(...\).

• Slower to type & frequently used: This isn't an uncommon problem in TeX. For instance, \mathbb{R} for the real numbers, or every environment's \begin{}...\end{}. You can consider these problems on a case-by-case basis: perhaps you'd define the macro \bbR for \mathbb{R}, use $...$ instead of \(...\), and grow a stomach for writing environments. Alternatively, you can find an editor that can fix all these problems at once, e.g. via a snippet engine.

• Harder to read than $...$: If your formula has a lot of parentheses and slashes, then it is harder to read:

  • \(f(x) = (x^2+1)/5\)
  • $f(x) = (x^2+1)/5$

  Changing the spacing can help:

  • \( f(x)=(x^2+1)/5 \)

  You can even go so far as to write

  \(
      f(x) = (x^2+1)/5      
  \)
  

  This amount of spacing might appear excessive, but as the complexity of the expression increases, separating it from the surrounding text becomes more and more desirable. This applies equally to $...$. Again, if you're acquainted with a good editor, you can minimize the amount of typing you actually have to do.

Answer 12

I prefer \(…\) to $…$ because emacs does a better job on highlighting the former than the latter. In particular, the visual feedback is so good that I don't remember latex complaining about errors due to unpaired \(…\). Ever.

Answer 13

The error reporting, the number of keystrokes, and the hooks into \(…\) have already been mentioned in other answers, so let us speak about highlighting. The default highlighting in emacs works somewhat differently for $…$ and \(…\) in the scope of \emph{…}:

The difference in highlighting is not only a question of taste (similar to the question of whether you like a BMW or a Mercedes more) but also important due to https://tex.stackexchange.com/a/59195. Apart from these details, there's not too much of a difference for a human typesetter. Personally, I switched from $…$ to \(…\) a few years ago and probably make less errors since then (though I got more proficient, I tend to think that the increased quality is also due to this switching).