What are brackets do in new command definition?

Question

In an article about defining new commands I saw an example

\newcommand{\R}{\mathbb{R}}
The set of real numbers are usually represented 
by a blackboard bold capital r: ( \R ).

What do brackets $ and $ do here? Are they required to call user-defined commands? But I am not using any brackets while using built-in commands like

\textbf{commands}

Can I write my custom command so that I can also use it without any brackets, like

\R

not

\( \R \)

$...$ is an alternative (newer) syntax for math mode, only available in latex, instead of TeX's $...$ . It provides a couple of extra checks. The command \mathbb can only be used in mathmode, so is needed when using this particular macro — Andrew Swann, Dec 19 '21 at 11:36
In the general case, you can search for it in the books. This one can be found in the LaTeX unofficial reference manual — user202729, Dec 19 '21 at 12:33

score 2 · Accepted Answer · answered Dec 19 '21 at 11:33

2

Typing $ \R $ is the same thing as typing $ \R $ , and the \mathbf command is allowed only in math mode. Therefore, you will get an error if you use it outside that mode.

answered Dec 19 '21 at 11:33

José Carlos Santos

4,803

2

That is not 100% correct,  gives better error messages than $... $ , sut since it is tedious to type most use $... $ – daleif Dec 19 '21 at 12:22
Why some things do work out of $ (like \textbf) and others do not (like new \R)? – Dims Dec 19 '21 at 15:10
That's another question. I suggest that you post it as such. – José Carlos Santos Dec 19 '21 at 15:15
Why? I need to define a command, which can be used WITHOUT $ and $, like textbf. It is second part of this question... – Dims Dec 19 '21 at 15:34
2

Indeed. You can define it as \newcommand{\R}{\ensuremath{\mathbb{R}}}. – José Carlos Santos Dec 19 '21 at 15:39

What are brackets do in new command definition?

1 Answers1