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% This file is public domain.
%
% Test symbolic equation references.
%
\ifx\eplain\undefined \input eplain \fi
\loggingall
\leftdisplays
An equation with a number in its name:
$$ a+b=1\eqdef{line1}$$
\line{did we mess up plain's line in equation \eqref{line1}?\hfil}
\bye
The first equation:
$$x + y = 1 \eqdef{first}$$
In equation \eqref{first}, we said that $x+y=1$.
Now, in equation \eqref{second}, we say that $a+b=2$.
$$a + b = 2 \eqdef{second}$$
The next equation is unlabeled in the output, but we can still refer to
it.
$$c + d = 3 \eqdefn{*}$$
And here's an equation whose text references another equation, namely,
\eqref{first}:
$$c=3\eqdef[\eqrefn{first}*]{first-star}$$
And a reference to it: \eqref{first-star}.
Here is the first of a group of equations: \eqdefn{group}
$$a = 1\eqsubdef{group-1}$$
and the invisible second, then the third of the group \eqsubdefn{group-invis}:
$$b = 2\eqsubdef{group-2}$$
We refer to the group as \eqref{group}, to the first as
\eqref{group-1}, the third as \eqref{group-2}, and the invisible second
as \eqref{group-invis}.
Here's an equation labeled strangely:
$$a=1\eqdef[\rm strange*]{foo}$$
And let's refer to \eqref{foo}.
Let's do subequations off that:
$$b=2\eqsubdef{foo-1}$$
And refer to it: \eqref{foo-1}.
% We can't use \count255, since #1 might involve contortions which
% trample it.
\newcount\subrefcount
\def\eqsubreftext#1#2{%
\subrefcount = #2
\advance\subrefcount by 96
#1\char\subrefcount
}
Let's try another group, with a different labelling scheme. Here is the
first of this group2: \eqdefn{group2}
$$a = 1\eqsubdef{group2-1}$$
and the second of the group2 \eqsubdefn{group2-invis}:
$$b = 2\eqsubdef{group2-2}$$
We refer to the group2 as \eqref{group2}, to the first as
\eqref{group2-1}, the third as \eqref{group2-2}, and the invisible second
as \eqref{group2-invis}.
Here is one done with displaylines:
% The \hfill's and \llap make the equation numbers come out in the right
% place if we are not doing \leftdisplays. (See the TeXbook, p.194.)
%$$\displaylines{
% \hfill x=1\hfill\llap{\eqdef{displayline-1}}\cr
% \hfill y=2\hfill\llap{\eqdef{displayline-2}}\cr
%}$$
$$\displaylines{
x=1\eqdef{displayline-1}\cr
y=2\eqdef{displayline-2}\cr
}$$
Let's refer to each of the equations in the displaylines:
\eqref{displayline-1}, \eqref{displayline-2}.
And one with eqalignno:
$$
\eqalignno{
a+b&=c&\eqdef{eqalign-1}\cr
d+e&=f&\eqdef{eqalign-2}\cr
}
$$
And one with leqalignno, and indented more:
{\leftdisplayindent = 1in
$$\leqalignno{
a+b &=c&\eqdef{leqalign-1}\cr
dt+eg&=f&\eqdef{leqalign-2}\cr
}$$
}
And now let's refer to those: \eqref{eqalign-1}, \eqref{eqalign-2},
\eqref{leqalign-1}, \eqref{leqalign-2}.
\def\eqprint#1{[\rm A.#1]}
From now on, all equation labels should be in brackets and preceded
by `A.'. In \eqref{*}, we said that $c+d=3$. And in equation
\eqref{undefined}, we say that $1+1=2$.
\eqdefn{*x}
\eqdefn{*y}
We defined equation \eqref{*y}, although we didn't give an equation for
it.
This is a forward reference to equation \eqref{forward}.
$$e + f = 4 \eqdef{forward}$$
That equation above defines \eqref{forward}.
\newcount\sectionnum \sectionnum = 1
\def\eqconstruct#1{\the\sectionnum.#1}
And now equation numbers should have a section number (which we start at
one) preceding them.
$$a+b=1 \eqdef{s-ab}$$
That equation is \eqref{s-ab}. The one we'll define in the next section
is \eqref{s-cd}.
\advance\sectionnum by 1
The equation in the previous section was \eqref{s-ab}. Let's define one
in this section:
$$c+d=3 \eqdef{s-cd}$$
And refer to it: \eqref{s-cd}.
\bye
|
