# [texhax] package

Uwe Lück uwe.lueck at web.de
Sat Nov 26 00:11:57 CET 2005

Nice ... no proposal yet? Joanne Snow's? [continued below]

At 15:38 23.11.05, Philip TAYLOR wrote:
>Joanne Snow asked the same question in 2003,
>but she did gloss the half-box :
>
> > Does anyone know how to type the half-box that that is used in actuarial
> > or financial math as part of the subscript for the present value of an
> > annuity?  I want to be able to type a subscript n with a half-box (top
> > and right side)"  around the n.  I have 2 awkward methods--neither of
> > which satisfies me.
> > Thanks.  Joanne Snow
>
>Philip Taylor
>--------
>Uwe Lück wrote:
> > Hello Wickes,
> >
> > At 07:17 21.11.05, Wickes Robbertse wrote:
> >
> >> I'm trying to find a command or package to facilitate actuarial
> >> notation in LaTex, i.e. for an ordinary annuity a_n the n is placed in
> >> a halfbox.

I've got this by boiling down LaTeX's \fbox:

\makeatletter
\newcommand{\annuity}[2]{%
\ensuremath{#1_{%
\setbox\@tempboxa\hbox{%
$\m at th\scriptstyle#2$\hskip\p@}%
\hbox{% !?!
\vbox{%
\hrule
\hbox{%
\vbox{%
\vskip\p@
\box\@tempboxa}%
\vrule}}}}}}
\makeatother
\begin{document}
\annuity{a}{n}

This may be my first proposal here that I've tested.
The \hbox marked with `!?!' seems to improve how the
rules meet -- curiously.

It is like a \fbox with \fboxsep=1pt -- I have no idea
whether this is appropriate.

More simple:

\makeatletter
\newcommand{\annuity}[2]{%
\ensuremath{#1_{%
\hbox{%
$\m at th\scriptstyle\overline{#2\hskip\p@}$\vrule}}}}
\makeatother
\begin{document}
\annuity{a}{n}

So I have two prosals as well. Again, \hskip\p@ is arbitrary.
It would be nice if the skip amount would be the distance
from overline rule to letter, i.e., 3 times the default rule
thickness as in TeXbook p. 443 Rule 9 -- I don't know how
to call the font under LaTeX of which it is \fontdimen8.
And it should be ensured that the \vrule is as thick as
the overline rule. And I cannot see from here at home
whether the two rules meet apropriately.

Good luck,
Uwe Lueck.