.\" Copyright (c) 1990 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"     @(#)eqn.1	6.4 (Berkeley) 6/26/90
.\"
.Dd June 26, 1990
.Dt EQN 1
.Os ATT 7th
.EQ
delim $$
.EN
.Sh NAME
.Nm eqn, neqn , checkeq
.Nd typeset mathematics
.Sh SYNOPSIS
.Nm eqn
.Oo
.Op Fl d Ar xy
.Op Fl p Ar n
.Op Fl s Ar n
.Op Fl f Ar n
.Op  file
\&...
.Nm checkeq
.Op  file
\&...
.Sh DESCRIPTION
.Nm Eqn
is a
.Xr troff 1
preprocessor
for typesetting mathematics
on a Graphic Systems phototypesetter,
.Xr neqn
on terminals.
Usage is almost always
.Pp
.Dl eqn file ... | troff
.Pp
.Dl neqn file ... | nroff
.Pp
If no files are specified,
these programs
read from the standard input.
A line beginning with `.EQ' marks the start of an equation;
the end of an equation
is marked by a line beginning with `.EN'.
Neither of these lines is altered,
so they may be defined in macro packages
to get
centering, numbering, etc.
It is also possible to set two characters as `delimiters';
subsequent text between delimiters is also treated as
.Nm eqn
input.
Delimiters may be set to characters
.Ar x
and
.Ar y
with the command-line argument
.Fl d xy
or (more commonly) with
`delim
.Ar xy  '
between .EQ and .EN.
The left and right delimiters may be identical.
Delimiters are turned off by `delim off'.
All text that is neither between delimiters nor between .EQ and .EN
is passed through untouched.
.Pp
The program
.Nm checkeq
reports missing or unbalanced delimiters and .EQ/.EN pairs.
.Pp
Tokens within
.Nm eqn
are separated by
spaces, tabs, newlines, braces, double quotes,
tildes or circumflexes.
Braces {} are used for grouping;
generally speaking,
anywhere a single character like
.Ar x
could appear, a complicated construction
enclosed in braces may be used instead.
Tilde ~ represents a full space in the output,
circumflex ^ half as much.
.Pp
.vs 13p
Subscripts and superscripts are produced with the keywords
.Ic sub
and
.Ic sup .
Thus
.Ar "x sub i"
makes
$x sub i$,
.Ar "a sub i sup 2"
produces
$a sub i sup 2$,
and
.Ar "e sup {x sup 2 +
.Ar y sup 2}"
gives
$e sup {x sup 2 + y sup 2}$.
.Pp
Fractions are made with
.Ic over :
.Ar "a over b"
yields $a over b$.
.Pp
.Ic sqrt
makes square roots:
.Ar "1 over sqrt
.Ar {ax sup 2 +bx+c}"
results in
$1 over sqrt {ax sup 2 +bx+c}$ .
.Pp
The keywords
.Ic from
and
.Ic to
introduce lower and upper limits on arbitrary things:
$lim from {n-> inf} sum from 0 to n x sub i$
is made with
.Ar "lim from {n\-> inf }
.Ar sum from 0 to n x
.Ar sub i."
.Pp
Left and right brackets, braces, etc., of the right height are made with
.Ic left
and
.Ic right :
.Op Ar "left
.Ar  x sup 2 + y sup 2
.AR over alpha right
.Ar \&~=~1"
produces
$left [ x sup 2 + y sup 2 over alpha right ] ~=~1$.
The
.Ic right
clause is optional.
Legal characters after
.Ic left
and
.Ic right
are braces, brackets, bars,
.Ic c
and
.Ic f
for ceiling and floor,
and "" for nothing at all (useful for a right-side-only bracket).
.Pp
Vertical piles of things are made with
.Ic pile  ,
.Ic lpile ,
.Ic cpile  ,
and
.Ic rpile  :
.Ar "pile {a above b above c}"
produces
$pile {a above b above c}$.
There can be an arbitrary number of elements in a pile.
.Ic lpile
left-justifies,
.Ic pile
and
.Ic cpile
center, with different vertical spacing,
and
.Ic rpile
right justifies.
.Pp
Matrices are made with
.Ic matrix  :
.Ar "matrix { lcol { x sub i
.Ar above y sub 2 } ccol {
.Ar 1 above 2 } }"
produces
$matrix { lcol { x sub i above y sub 2 } ccol { 1 above 2 } }$.
In addition, there is
.Ic rcol
for a right-justified column.
.Pp
.vs 12p
Diacritical marks are made with
.Ic dot  ,
.Ic dotdot ,
.Ic hat  ,
.Ic tilde ,
.Ic bar  ,
.Ic vec ,
.Ic dyad  ,
and
.Ic under  :
.Ar "x dot \&= f(t) bar"
is
$x dot = f(t) bar$,
.Ar "y dotdot bar \&~=~
.Ar n under"
is
$y dotdot bar ~=~ n under$,
and
.Ar "x vec \&~=~ y dyad"
is
$x vec ~=~ y dyad$.
.Pp
Sizes and font can be changed with
.Ic size
.Op Ar n
or
.Ic size
.Sf Sy \(+- n,
.Ic roman  ,
.Ic italic ,
.Ic bold  ,
and
.Ic font
.Ar n.
Size and fonts can be changed globally in a document by
.Ic gsize
.Ar n
and
.Ic gfont
.Ar n ,
or by the command-line arguments
.Cx Fl s
.Ar n
.Cx
and
.Cx Fl f
.Ar n
.Cx .
.Cx
.Pp
Normally subscripts and superscripts are reduced by
3 point sizes from the previous size;
this may be changed by the command-line argument
.Cx Fl p
.Ar n .
.Cx
.Pp
Successive display arguments can be lined up.
Place
.Ic mark
before the desired lineup point in the first equation;
place
.Ic lineup
at the place that is to line up vertically in subsequent equations.
.Pp
Shorthands may be defined
or existing keywords redefined with
.Ic define  :
.Ar "define thing \&% replacement \&%"
defines a new token called
.Ar thing
which will be replaced by
.Ar replacement
whenever it appears thereafter.
The
.Ic \&%
may be any character that does not occur in
.Ar replacement .
.Pp
Keywords like
.Ar sum
.EQ
( sum )
.EN
.Ar int
.EQ
( int )
.EN
.Ar inf
.EQ
( inf )
.EN
and shorthands like
>=
.EQ
(>=)
.EN
\->
.EQ
(->),
.EN
and
!=
.EQ
( != )
.EN
are recognized.
Greek letters are spelled out in the desired case, as in
.Ar alpha
or
.Ar GAMMA .
Mathematical words like sin, cos, log are made Roman automatically.
.Xr Troff  1
four-character escapes like \e(bs (\(bs)
can be used anywhere.
Strings enclosed in double quotes "..."
are passed through untouched;
this permits keywords to be entered as text,
and can be used to communicate
with
.Xr troff 1
when all else fails.
.Sh SEE ALSO
.Xr troff 1 ,
.Xr tbl 1 ,
.Xr ms 7 ,
.Xr eqnchar 7
.br
B. W. Kernighan and L. L. Cherry,
.Em Typesetting Mathematics\-User's Guide
.Br
J. F. Ossanna,
.Em NROFF/TROFF User's Manual
.Sh HISTORY
.Nm Eqn
appeared in Version 6 AT&T Unix.
.Sh BUGS
.Pp
To embolden digits, parens, etc.,
it is necessary to quote them,
as in `bold "12.3"'.