
EQN(1) EQN(1)
delim $$
NAME
eqn  typeset mathematics
SYNOPSIS
eqn [ option ... ] [ file ... ]
DESCRIPTION
Eqn is a troff(1) preprocessor for typesetting mathematics on a typesetter. Usage is
almost always
eqn file ...  troff
If no files are specified, eqn reads from the standard input. Eqn prepares output for the
typesetter named in the Tdest option (default Tutf; see troff(1)). When run with other
preprocessor filters, eqn usually comes last.
A line beginning with .EQ marks the start of an equation; the end of an equation is marked
by a line beginning with .EN. Neither of these lines is altered, so they may be defined
in macro packages to get centering, numbering, etc. It is also possible to set two char
acters as `delimiters'; text between delimiters is also eqn input. Delimiters may be set
to characters x and y with the option dxy or (more commonly) with delim xy between .EQ
and .EN. Left and right delimiters may be identical. (They are customarily taken to be
$font L "$$" )$. Delimiters are turned off by All text that is neither between delimiters
nor between .EQ and .EN is passed through untouched.
Tokens within 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 could appear, a complicated construction enclosed in braces may be used
instead. Tilde represents a full space in the output, circumflex half as much.
Subscripts and superscripts are produced with the keywords sub and sup. Thus makes $x sub
i$, produces $a sub i sup 2$, and gives $e sup {x sup 2 + y sup 2}$.
Over makes fractions: yields $a over b$.
Sqrt produces square roots: results in $1 over sqrt {ax sup 2 +bx+c}$ .
The keywords from and to introduce lower and upper limits on arbitrary things: $lim from
{n > inf} sum from 0 to n x sub i$ is made with
Left and right brackets, braces, etc., of the right height are made with left and right:
produces $left [ x sup 2 + y sup 2 over alpha right ] ~=~1$. The right clause is
optional. Legal characters after left and right are braces, brackets, bars, c and f for
ceiling and floor, and "" for nothing at all (useful for a rightsideonly bracket).
Vertical piles of things are made with pile, lpile, cpile, and rpile: produces $pile {a
above b above c}$. There can be an arbitrary number of elements in a pile. lpile left
justifies, pile and cpile center, with different vertical spacing, and rpile right justi
fies.
Matrices are made with matrix: produces $matrix { lcol { x sub i above y sub 2 } ccol { 1
above 2 } }$. In addition, there is rcol for a rightjustified column.
Diacritical marks are made with prime, dot, dotdot, hat, tilde, bar, under, vec, dyad, and
under: is $x sub 0 sup prime = f(t) bar + g(t) under$, and is $x vec = y dyad$.
Sizes and fonts can be changed with prefix operators size n, size +n, fat, roman, italic,
bold, or font n. Size and fonts can be changed globally in a document by gsize n and
gfont n, or by the commandline arguments sn and fn.
Normally subscripts and superscripts are reduced by 3 point sizes from the previous size;
this may be changed by the commandline argument pn.
Successive display arguments can be lined up. Place mark before the desired lineup point
in the first equation; place lineup at the place that is to line up vertically in subse
quent equations.
Shorthands may be defined or existing keywords redefined with define: thing replacement
defines a new token called thing which will be replaced by replacement whenever it appears
thereafter. The may be any character that does not occur in
Keywords like ( sum ), ( int ), ( inf ), and shorthands like (>=), (>), and ( != ) are
recognized. Greek letters are spelled out in the desired case, as in or Mathematical
words like are made Roman automatically. Troff(1) fourcharacter escapes like (<=) 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 troff when all
else fails.
FILES
/sys/lib/troff/font/devutf
font descriptions for PostScript
SOURCE
/sys/src/cmd/eqn
SEE ALSO
troff(1), tbl(1)
J. F. Ossanna and B. W. Kernighan, ``Troff User's Manual''.
B. W. Kernighan and L. L. Cherry, ``Typesetting MathematicsUser's Guide'', Unix Research
System Programmer's Manual, Tenth Edition, Volume 2.
BUGS
To embolden digits, parens, etc., it is necessary to quote them, as in delim off
EQN(1) 
