I'm trying a simple definition of a set.
My try: $M=\{x\,|\,1\le x\le p-2\}$
Is there a more comfortable way of getting a little space before and after the |
? I'm thinking of something like the \mod
which does the spacing on its own.
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Sign up to join this communityI'm trying a simple definition of a set.
My try: $M=\{x\,|\,1\le x\le p-2\}$
Is there a more comfortable way of getting a little space before and after the |
? I'm thinking of something like the \mod
which does the spacing on its own.
The vertical bar is usually produced by using \mid
, which prints the same symbol as |
(or \vert
, which is a synonym).
The difference is that \mid
is treated as a relation symbol, so it will have thick spaces on its sides:
$M = \{ x \mid 1 \le x \le p-2 \}$
Many people (including Knuth) recommend adding thin spaces in order to detach the braces when using a condition with \mid
:
$M = \{\, x \mid 1 \le x \le p-2 \,\}$
but
$X = \{1,2,3,4\}
when listing elements. Take your pick. For a small number of set denotations in the document this should not be a problem; but when there are many of them it's better to add a command, in order to ensure uniformity:
\newcommand{\Set}[2]{%
\{\, #1 \mid #2 \, \}%
}
(the %
aren't really necessary in this case) so you can call
$M = \Set{x}{1\le x\le p-2}$
and forget about the details. You'll also have the advantage that, if a fussy copy editor says they want colons and not vertical bars, it will be just a matter of changing \mid
into :
in the definition of \Set
.
In a paper I was fine tuning for publication in a conference proceedings volume, sets were denoted in three different ways: sometimes the separation was with the bar, sometimes with a colon, sometimes with a semicolon. Being consistent in notation is a necessity, not an option.
An interesting option for you may be to load the braket package and use its commands \set
and \Set
. The lowercase-spelled version, \set
, uses fixed-size (small) curly braces and central vertical bars; the uppercase-spelled version lets the "fence" symbols grow automatically with the material they enclose.
You could thus enter an expression such as
$M=\set{x|1\le x\le p-2}$
and let the package do the job of formatting the expression properly.
\mid
:\{x\mid 1\le x\le p-2\}
. Many people add thin spaces (that is,\,
) after\{
and before\}
when using\mid
. – egreg Sep 5 '13 at 8:48\mod
in fact:\mid
:-) – David Carlisle Sep 5 '13 at 8:48