The Comprehensive LaTeX Symbol List - CTAN

A related L ATEX command, borrowed from Plain TEX, is \ooalign. \ooalign vertically overlaps symbols and
works both within and outside of math mode. Essentially, it creates a single-column tabular environment with
zero vertical distance between rows. However, because it is based directly on TEX’s \ialign primitive, \ooalign
uses TEX’s tabular syntax instead of L ATEX’s (i.e., with \cr as the row terminator instead of \\). The following
example of \ooalign, a macro that defines a standard-state symbol (\stst, “ −◦ ”) as a superscripted Plimsoll
line (\barcirc, “−◦ ”), 9 is due to an October 2007 comp.text.tex post by Donald Arseneau:
\makeatletter
\providecommand\barcirc{\mathpalette\@barred\circ}
\def\@barred#1#2{\ooalign{\hfil$#1-$\hfil\cr\hfil$#1#2$\hfil\cr}}
\newcommand\stst{^{\protect\barcirc}}
\makeatother
In the preceding code, note the \ooalign call’s use of \hfil to horizontally center a minus sign (“−”) and a
\circ (“◦”).
As another example of \ooalign, consider the following code (due to Enrico Gregorio in a June 2007 post to
comp.text.tex) that overlaps a \ni (“∋”) and two minus signs (“ −”) to produce “∋−”, an obscure variation on
the infrequently used “3” symbol for “such that”discussed on page 113:
\newcommand{\suchthat}{%
\mathrel{\ooalign{$\ni$\cr\kern-1pt$-$\kern-6.5pt$-$}}}
The slashed package, although originally designed for producing Feynman slashed-character notation, in fact
facilitates the production of arbitrary overlapped symbols. The default behavior is to overwrite a given character
with “/”. For example, \slashed{D} produces “ /D”. However, the \declareslashed command provides the
flexibility to specify the mathematical context of the composite character (operator, relation, punctuation, etc.,
as will be discussed in Section 8.4), the overlapping symbol, horizontal and vertical adjustments in symbolrelative
units, and the character to be overlapped. Consider, for example, the symbol for reduced quadrupole
moment (“-I”). This can be declared as follows:
\newcommand{\rqm}{{%
\declareslashed{}{\text{-}}{0.04}{0}{I}\slashed{I}}}
\declareslashed{·}{·}{·}{·}{I} affects the meaning of all subsequent \slashed{I} commands in the same
scope. The preceding definition of \rqm therefore uses an extra set of curly braces to limit that scope to a single
\slashed{I}. In addition, \rqm uses amstext’s \text macro (described on page 117) to make \declareslashed
use a text-mode hyphen (“-”) instead of a math-mode minus sign (“−”) and to ensure that the hyphen scales
properly in size in subscripts and superscripts. See slashed’s documentation (located in slashed.sty itself) for a
detailed usage description of the \slashed and \declareslashed commands.
Somewhat simpler than slashed is the centernot package. centernot provides a single command, \centernot,
which, like \not, puts a slash over the subsequent mathematical symbol. However, instead of putting the slash
at a fixed location, \centernot centers the slash over its argument. \centernot might be used, for example, to
create a “does not imply” symbol:
=⇒ \not\Longrightarrow
See the centernot documentation for more information.
vs.
=⇒ \centernot\Longrightarrow
9 While \barcirc illustrates how to combine symbols using \ooalign, the stmaryrd package’s \minuso command (Table 46 on
page 25) provides a similar glyph (“”) as a single, indivisible symbol.
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