```delim \$\$

NAME
eqn  -  typeset mathematics

SYNOPSIS
eqn [ file ] ...

DESCRIPTION
Eqn  is a troff(I) preprocessor for typesetting mathematics
on the Graphics Systems phototypesetter.   Usage  is  almost
always

eqn file ... | troff

If  no  files are specified, eqn reads from the standard in-
put.  A line beginning with ``.EQ'' marks the  start  of  an
equation;  the end of an equation is marked by a line begin-
ning with ``.EN''.  Neither of these lines is altered or de-
fined by eqn, so you can define them yourself to get center-
ing, numbering, etc.  All other lines are  treated  as  com-
ments, and passed through untouched.

Spaces,  tabs,  newlines,  braces,  double quotes, tilde and
circumflex are the only delimiters.  Braces ``{}'' are  used
for  grouping.   Use  tildes ``~'' to get extra spaces in an
equation.

Subscripts and superscripts are produced with  the  keywords
sub  and  sup.   Thus x sub i makes \$x sub i\$, a sub i sup 2
produces \$a sub i sup 2\$, and e sup {x sup 2 + y sup 2}
gives  \$e sup {x sup 2 + y sup 2}\$.  Fractions are made with
over. a over b is \$a over b\$ and 1 over sqrt {ax sup 2
+bx+c}  is  \$1  over  sqrt  {ax  sup 2 +bx+c}\$ .  sqrt makes
square roots.

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 lim from {n-> inf} sum from 0 to n x sub i.
Left  and  right brackets, braces, etc., of the right height
are made with left and right: left [ x sup 2 + y sup 2 over
alpha right ] ~=~1 produces \$left [ x sup 2 + y sup 2 over
alpha right ] ~=~1\$.  The right clause is optional.

Vertical piles of things are made with pile, lpile, cpile,
and  rpile: pile {a above b above c} 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  justifies.

Diacritical marks are made with dot, dotdot, hat, bar: x dot
= f(t) bar is \$x dot = f(t) bar\$.  Default sizes  and  fonts
can be changed with size n and various of roman, italic, and
bold.

Keywords like sum ( sum ) int ( int ) inf ( inf ) and short-
hands  like  >=  (>=)  ->  (->),  != ( != ), are recognized.
Spell out Greek letters in the desired case,  as  in  alpha,
GAMMA.  Mathematical words like sin, cos, log are made Roman
automatically.  Troff(I) four-character escapes  like  \(ci
(O) can be used anywhere.  Strings enclosed in double quotes

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EQN(I)                       2/22/74                       EQN(I)

"..."  are passed through untouched.

SEE ALSO
A System for Typesetting Mathematics (Computer Science Tech-
nical Report #17, Bell Laboratories, 1974.)
TROFF Users' Manual (internal memorandum)
TROFF Made Trivial (internal memorandum)
troff(I), neqn(I)

BUGS
Undoubtedly.   Watch  out  for  small or large point sizes -
it's tuned too well for size 10.  Be cautious  if  inserting
horizontal or vertical motions, and of backslashes in gener-
al.  delim off

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