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EQN(1)									EQN(1)

NAME
eqn - format equations for troff

SYNOPSIS
eqn [ -rvCNR ] [	-dxy ] [ -Tname	] [ -Mdir ] [ -fF ] [ -sn ] [ -pn ]
[ -mn ] [ files... ]

It is possible to have whitespace between a command line	option and its
parameter.

DESCRIPTION
This manual page	describes the GNU version of eqn, which	is part	of the
groff document formatting system.  eqn compiles descriptions  of	 equa-
tions  embedded	within troff input files into commands that are	under-
stood by	troff.	Normally, it should be invoked using the -e option  of
groff.	The  syntax  is	quite compatible with Unix eqn.	 The output of
GNU eqn cannot be processed with	Unix troff; it must be processed  with
GNU  troff.   If	 no  files are given on	the command line, the standard
input will be read.  A filename of - will cause the standard  input  to
be read.

eqn  searches  for  the file eqnrc in the directories given with	the -M
option first, then in /usr/share/tmac, /usr/share/tmac, and finally  in
the  standard  macro directory /usr/share/tmac.	If it exists, eqn will
process it before the other input files.	 The -R	option prevents	 this.

GNU eqn does not	provide	the functionality of neqn: it does not support
low-resolution, typewriter-like devices	(although  it  may  work  ade-
quately for very	simple input).

OPTIONS
-dxy   Specify  delimiters  x and y for the left	and right end, respec-
tively, of in-line  equations.   Any  delim  statements  in  the
source file overrides this.

-C     Recognize	 .EQ  and  .EN even when followed by a character other
than space or newline.

-N     Don't allow newlines within delimiters.  This option allows  eqn
to recover better	from missing closing delimiters.

-v     Print the	version	number.

-r     Only one size reduction.

-mn    The  minimum  point-size	is n.  eqn will	not reduce the size of
subscripts or superscripts to a smaller size than	n.

-Tname The output is for	device name.  The only effect of  this	is  to
define a macro name with a value of 1.  Typically	eqnrc will use
this to provide definitions appropriate for the  output  device.
The default output device	is ps.

-Mdir  Search dir for eqnrc before the default directories.

-R     Don't load eqnrc.

-fF    This is equivalent to a gfont F command.

-sn    This  is equivalent to a gsize n command.	 This option is	depre-
cated.  eqn will normally	set equations at whatever the  current
point size is when the equation is encountered.

-pn    This  says  that	subscripts and superscripts should be n	points
smaller than the surrounding text.  This option  is  deprecated.
Normally	eqn  makes  sets subscripts and	superscripts at	70% of
the size of the surrounding text.

USAGE
Only the	differences between GNU	eqn and	Unix eqn are described here.

Most of the new features	of GNU eqn are based on	TeX.  There  are  some
references  to the differences between TeX and GNU eqn below; these may
safely be ignored if you	do not know TeX.

Automatic spacing
eqn gives each component	of an equation a type, and adjusts the spacing
between components using	that type.  Possible types are:

ordinary	   an ordinary character such as 1' or	x';
_
operator	   a large operator such as _';

binary	   a binary operator such as +';

relation	   a relation such as =';

opening	   a opening bracket such as (';

closing	   a closing bracket such as )';

punctuation  a punctuation character such	as ,';

inner	   a subformula	contained within brackets;

suppress	   spacing  that  suppresses automatic spacing adjust-
ment.

Components of an	equation get a type in one of two ways.

type t e
This yields an equation component	that contains e	but  that  has
type  t, where t is one of the types mentioned above.  For exam-
ple, times is defined as

type "binary" \(mu

The name of the type doesn't have	to be quoted, but quoting pro-
tects from macro expansion.

chartype	t text
Unquoted groups of characters are	split up into individual char-
acters, and the type  of	each  character	 is  looked  up;  this
changes the type that is stored for each character; it says that
the characters in	text from now on have type t.  For example,

chartype "punctuation" .,;:

would make the characters	.,;:' have type punctuation  whenever
they  subsequently appeared in an	equation.  The type t can also
be letter	or digit; in these cases  chartype  changes  the  font
type of the characters.  See the Fonts subsection.

New primitives
e1 smallover e2
This  is	similar	 to over; smallover reduces the	size of	e1 and
e2; it also puts less vertical space between e1 or  e2  and  the
fraction	bar.   The over	primitive corresponds to the TeX \over
primitive	in display styles; smallover corresponds to  \over  in
non-display styles.

vcenter e
This vertically centers e	about the math axis.  The math axis is
the vertical position about which	characters such	as +' and -'
are  centered; also it is	the vertical position used for the bar
of fractions.  For example, sum is defined as

{ type "operator" vcenter size +5 \(*S }

e1 accent e2
This sets	e2 as an accent	over e1.  e2 is	assumed	to be  at  the
correct  height  for  a  lowercase letter; e2 will be moved down
according	if e1 is taller	or shorter than	 a  lowercase  letter.
For example, hat is defined as

accent { "^" }

dotdot,  dot,  tilde,  vec,  and dyad are	also defined using the
accent primitive.

e1 uaccent e2
This sets	e2 as an accent	under e1.  e2 is assumed to be at  the
correct  height  for a character without a descender; e2 will be
moved down if e1 has a descender.	 utilde	is  pre-defined	 using
uaccent as a tilde accent	below the baseline.

split "text"
This has the same	effect as simply

text

but text is not subject to macro expansion because it is quoted;
text will	be split up and	the spacing between individual charac-
ters will	be adjusted.

nosplit text
This has the same	effect as

"text"

but  because  text  is  not  quoted  it will be subject to macro
expansion; text will not be split	up  and	 the  spacing  between
individual characters will not be	adjusted.

e opprime
This  is	a  variant of prime that acts as an operator on	e.  It
produces a different  result  from  prime	 in  a	case  such  as
A	opprime	sub 1:	with  opprime  the  1 will be tucked under the
prime as a subscript to the A (as	is conventional	in  mathemati-
cal  typesetting),  whereas with prime the 1 will	be a subscript
to the prime character.  The precedence of opprime is  the  same
as  that	of  bar	and under, which is higher than	that of	every-
thing except accent and uaccent.	In unquoted text a '  that  is
not the first character will be treated like opprime.

special text e
This constructs a	new object from	e using	a troff(1) macro named
text.  When the macro is called, the string 0s will contain  the
output  for  e, and the number registers 0w, 0h, 0d, 0skern, and
0skew will contain the width, height, depth, subscript kern, and
skew  of	e.   (The  subscript kern of an	object says how	much a
subscript	on that	object should be tucked	in;  the  skew	of  an
object  says how far to the right	of the center of the object an
accent over the object should be placed.)	 The macro must	modify
0s  so that it will output the desired result with its origin at
the current point, and increase the current horizontal  position
by  the  width of	the object.  The number	registers must also be
modified so that they correspond to the result.

For example, suppose you wanted a	construct  that	 cancels'  an
expression by drawing a diagonal line through it.

.EQ
define cancel 'special Ca'
.EN
.de Ca
.	ds 0s \
\Z'\\*(0s'\
\v'\\n(0du'\
\D'l \\n(0wu -\\n(0hu-\\n(0du'\
\v'\\n(0hu'
..

Then you could cancel an expression e with cancel	{ e }

Here's  a	 more  complicated construct that draws	a box round an
expression:

.EQ
define box	'special Bx'
.EN
.de Bx
.	ds 0s \
\Z'\h'1n'\\*(0s'\
\Z'\
\v'\\n(0du+1n'\
\D'l \\n(0wu+2n 0'\
\D'l 0 -\\n(0hu-\\n(0du-2n'\
\D'l -\\n(0wu-2n 0'\
\D'l 0 \\n(0hu+\\n(0du+2n'\
'\
\h'\\n(0wu+2n'
.	nr 0w +2n
.	nr 0d +1n
.	nr 0h +1n
..

space n
A	positive value of the integer n	(in hundredths of an em)  sets
the  vertical spacing before the equation, a negative value sets
the spacing after	the equation, replacing	 the  default  values.
This  primitive  provides	an interface to	groff's	\x escape (but
with opposite sign).

This keyword has no effect if the	equation is part of a pic pic-
ture.

Extended primitives
col n { ... }
ccol n {	... }
lcol n {	... }
rcol n {	... }
pile n {	... }
cpile n { ... }
lpile n { ... }
rpile n { ... }
The  integer value n (in hundredths of an	em) increases the ver-
tical spacing between rows, using	groff's	\x  escape.   Negative
values are possible but have no effect.  If there	is more	than a
single value given in a matrix, the biggest one is used.

Customization
The appearance of equations is controlled by a large number of  parame-
ters.  These can	be set using the set command.

set p n
This sets	parameter p to value n;	n is an	integer.  For example,

set x_height 45

says that	eqn should assume an x height of 0.45 ems.

Possible parameters are as follows.  Values are in units of hun-
dredths  of  an  em unless otherwise stated.  These descriptions
are intended to be expository rather than	definitive.

minimum_size
eqn will not set anything at a  smaller  point-size  than
this.  The	value is in points.

fat_offset
The  fat  primitive emboldens an equation by overprinting
two copies	of the equation	horizontally  offset  by  this
amount.

over_hang
A	fraction  bar will be longer by	twice this amount than
the maximum of the	widths of the numerator	and  denomina-
tor;  in  other words, it will overhang the numerator and
denominator by at least this amount.

accent_width
When bar or under is applied to a single  character,  the
line  will	be this	long.  Normally, bar or	under produces
a line whose length is the	width of the object  to	 which
it	applies; in the	case of	a single character, this tends
to	produce	a line that looks too long.

delimiter_factor
Extensible	delimiters produced with the  left  and	 right
primitives	 will  have  a combined	height and depth of at
least this	many thousandths of twice the  maximum	amount
by	 which	the  sub-equation  that	the delimiters enclose
extends away from the axis.

delimiter_shortfall
Extensible	delimiters produced with the  left  and	 right
primitives	will have a combined height and	depth not less
than the difference of twice the maximum amount by	 which
the sub-equation that the delimiters enclose extends away
from the axis and this amount.

null_delimiter_space
This much horizontal space	is inserted on each side of  a
fraction.

script_space
The  width	of subscripts and superscripts is increased by
this amount.

thin_space
This amount of  space  is	automatically  inserted	 after
punctuation characters.

medium_space
This  amount of space is automatically inserted on	either
side of binary operators.

thick_space
This amount of space is automatically inserted on	either
side of relations.

x_height
The height	of lowercase letters without ascenders such as
x'.

axis_height
The height	above the baseline of the center of characters
such  as +' and `-'.  It is important that this value is
correct for the font you are using.

default_rule_thickness
This should set to	the thickness of the  \(ru  character,
or	the thickness of horizontal lines produced with	the \D
escape sequence.

num1   The over command will shift up the	numerator by at	 least
this amount.

num2   The  smallover  command will shift	up the numerator by at
least this	amount.

denom1 The over command will shift down the  denominator	by  at
least this	amount.

denom2 The  smallover command will shift down the	denominator by
at	least this amount.

sup1   Normally superscripts will	be shifted up by at least this
amount.

sup2   Superscripts  within  superscripts	 or  upper  limits  or
numerators	of smallover fractions will be shifted	up  by
at	least this amount.  This is usually less than sup1.

sup3   Superscripts  within denominators or square roots or sub-
scripts or	lower limits will be shifted up	 by  at	 least
this amount.  This	is usually less	than sup2.

sub1   Subscripts	will normally be shifted down by at least this
amount.

sub2   When there	is both	a subscript  and  a  superscript,  the
subscript will be shifted down by at least	this amount.

sup_drop
The  baseline  of a superscript will be no	more than this
much amount below the top of  the	object	on  which  the
superscript is set.

sub_drop
The  baseline  of	a subscript will be at least this much
below the bottom of the object on which the subscript  is
set.

big_op_spacing1
The baseline of an	upper limit will be at least this much
above the top of the object on which the limit is set.

big_op_spacing2
The baseline of a lower limit will	be at least this  much
below the bottom of the object on which the limit is set.

big_op_spacing3
The bottom	of an upper limit will be at least  this  much
above the top of the object on which the limit is set.

big_op_spacing4
The top of	a lower	limit will be at least this much below
the bottom	of the object on which the limit is set.

big_op_spacing5
This much vertical	space will be added  above  and	 below
limits.

baseline_sep
The  baselines  of	the rows in a pile or matrix will nor-
mally be this far apart.  In most cases  this  should  be
equal to the sum of num1 and denom1.

shift_down
The  midpoint  between  the  top  baseline	and the	bottom
baseline in a matrix or pile will be shifted down by this
much  from	 the axis.  In most cases this should be equal
to	axis_height.

column_sep
This much space  will  be	added  between	columns	 in  a
matrix.

matrix_side_sep
This much space will be added at each side	of a matrix.

draw_lines
If	 this  is  non-zero,  lines will be drawn using	the \D
escape sequence, rather than with the \l escape  sequence
and the \(ru character.

body_height
The  amount  by  which the	height of the equation exceeds
this will be added	as extra space before  the  line  con-
taining  the  equation  (using \x).  The default value is
85.

body_depth
The amount	by which the depth  of	the  equation  exceeds
this will be added	as extra space after the line contain-
ing the equation (using \x).  The default value is	35.

nroff  If	this is	non-zero, then ndefine will behave like	define
and  tdefine  will	 be  ignored,  otherwise  tdefine will
behave like define	and  ndefine  will  be	ignored.   The
default value is 0	(This is typically changed to 1	by the
eqnrc file	 for  the  ascii,  latin1,  utf8,  and	cp1047
devices.)

A	 more precise description of the role of many of these parame-
ters can be found	in Appendix H of The TeXbook.

Macros
Macros can take arguments.  In a	macro body, \$n where n	is  between  1
and  9,	will  be  replaced by the n-th argument	if the macro is	called
with arguments; if there	 are  fewer  than  n  arguments,  it  will  be
replaced	 by  nothing.	A word containing a left parenthesis where the
part of the word	before the left	parenthesis has	been defined using the
define command will be recognized as a macro call with arguments; char-
acters following	the left parenthesis up	to a matching right  parenthe-
sis  will be treated as comma-separated arguments; commas inside	nested
parentheses do not terminate an argument.

sdefine name X anything X
This is like the define command, but name	will not be recognized
if called	with arguments.

include "file"
copy "file"
Include  the  contents  of file (include and copy	are synonyms).
Lines of file beginning with .EQ or .EN will be ignored.

ifdef name X anything X
If name has been defined by define (or  has  been	 automatically
defined  because	name  is  the output device) process anything;
otherwise	ignore anything.  X can	be any character not appearing
in anything.

undef name
Remove definition	of name, making	it undefined.

Besides	the  macros  mentioned	above,	the  following definitions are
available: Alpha, Beta, ..., Omega (this	is the same  as	 ALPHA,	 BETA,
..., OMEGA), ldots (three dots on the base line), and dollar.

Fonts
eqn normally uses at least two fonts to set an equation:	an italic font
for letters, and	a roman	font for everything else.  The existing	 gfont
command	changes	 the font that is used as the italic font.  By default
this is I.  The font that is used as the	 roman	font  can  be  changed
using the new grfont command.

grfont f
Set the roman font to f.

The  italic  primitive  uses  the current italic	font set by gfont; the
roman primitive uses the	current	roman font set by  grfont.   There  is
also  a	new  gbfont  command,  which changes the font used by the bold
primitive.  If you only use the roman, italic and  bold	primitives  to
changes	fonts within an	equation, you can change all the fonts used by
your equations just by using gfont, grfont and gbfont commands.

You can control which characters	are treated as letters (and  therefore
set  in italics)	by using the chartype command described	above.	A type
of letter will cause a character	to be set in italic type.  A  type  of
digit will cause	a character to be set in roman type.

FILES
/usr/share/tmac/eqnrc  Initialization file.

BUGS
Inline  equations  will be set at the point size	that is	current	at the
beginning of the	input line.

SEE ALSO
groff(1), troff(1), pic(1), groff_font(5), The TeXbook

Groff Version 1.19.2		3 December 2012				EQN(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | USAGE | FILES | BUGS | SEE ALSO

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