The Comprehensive LaTeX Symbol List - CTAN

Producing complex accents
Accents are a special case of combining existing symbols to make new symbols. While various tables in this
document show how to add an accent to an existing symbol, some applications, such as transliterations from non-
Latin alphabets, require multiple accents per character. For instance, the creator of pdfTEX writes his name as
“Hàn Th ´ ê Thành”. The dblaccnt package enables LATEX to stack accents, as in “H\‘an Th\’{\^e} Th\‘anh” (albeit
not in the OT1 font encoding). In addition, the wsuipa package defines \diatop and \diaunder macros for putting
one or more diacritics or accents above or below a given character. For example, \diaunder[{\diatop[\’|\=]}|
\textsubdot{r}] produces “´¯r ”. See the wsuipa documentation for more information.
The accents package facilitates ˙ the fabrication of accents in math mode. Its \accentset command enables any
character to be used as an accent. For instance, \accentset{\star}{f} produces “ ⋆
f ” and \accentset{e}{X}
produces “ e
X”. \underaccent does the same thing, but places the accent beneath the character. This enables
constructs like \underaccent{\tilde}{V}, which produces “ V ”. accents provides other accent-related features
as well; see the documentation for more information.
˜
Creating extensible symbols
A relatively simple example of creating extensible symbols stems from a comp.text.tex post by Donald Arseneau
(June 2003). The following code defines an equals sign that extends as far to the right as possible, just like L ATEX’s
\hrulefill command:
\makeatletter
\def\equalsfill{$\m@th\mathord=\mkern-7mu
\cleaders\hbox{$\!\mathord=\!$}\hfill
\mkern-7mu\mathord=$}
\makeatother
TEX’s \cleaders and \hfill primitives are the key to understanding \equalsfill’s extensibility. Essentially,
\equalsfill repeats a box containing “=” plus some negative space until it fills the maximum available horizontal
space. \equalsfill is intended to be used with LATEX’s \stackrel command, which stacks one mathematical
expression (slightly reduced in size) atop another. Hence, “\stackrel{a}{\rightarrow}” produces “ a →” and “X
\stackrel{\text{definition}}{\hbox{\equalsfill}} Y” produces “X definition
======= Y ”.
If all that needs to extend are horizontal and vertical lines—as opposed to repeated symbols such as the “=”
in the previous example—LATEX’s array or tabular environments may suffice. Consider the following code (due
to a February 1999 comp.text.tex post by Donald Arseneau and subsequent modifications by Billy Yu and Scott
Pakin) for typesetting annuity and life-insurance symbols:
\DeclareRobustCommand{\actuarial}[2][]{%
\def\arraystretch{0}%
\setlength\arraycolsep{0.5pt}%
\setlength\arrayrulewidth{0.5pt}%
\setbox0=\hbox{$\scriptstyle#1#2$}%
\begin{array}[b]{*2{@{}>{\scriptstyle}c}|}
\cline{2-2}%
\rule[1.25pt]{0pt}{\ht0}%
#1 & #2%
\end{array}%
}
Using the preceding definition, one can type, e.g., “$a_{\actuarial{n}}$” to produce “an ” and
“$a_{\actuarial[x:]{n}}$” to produce “ax:n ”
A more complex example of composing accents is the following definition of extensible \overbracket,
\underbracket, \overparenthesis, and \underparenthesis symbols, taken from a May 2002 comp.text.tex
post by Donald Arseneau:
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