EQN(1)							      General Commands Manual							    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 characters as
       `delimiters'; text between delimiters is also eqn input.  Delimiters may be set to characters x and y with the option -dxy  or  (more  com-
       monly)  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 right-side-only 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 num-
       ber of elements in a pile.  lpile left-justifies, pile and cpile center, with different vertical spacing, and rpile right justifies.

       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
       right-justified 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 command-line arguments -sn and -fn.

       Normally  subscripts and superscripts are reduced by 3 point sizes from the previous size; this may be changed by the command-line 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 subsequent 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) four-character escapes like (<=) can be used any-
       where.  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 Mathematics--User's Guide'', Unix Research System Programmer's Manual, Tenth Edition, Vol-
       ume 2.

BUGS

       To embolden digits, parens, etc., it is necessary to quote them, as in delim off

																	    EQN(1)