# RedHat 9 (Linux i386)(redhat section 1)man page for geqn

EQN(1)							      General Commands Manual							    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
equations embedded within troff input files into commands that are understood 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

eqn searches for the file eqnrc in the directories given with the -M option first, then in /usr/lib/groff/site-tmac, /usr/share/groff/site-
tmac, and finally in the standard macro directory /usr/share/groff/1.18.1/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, respectively, 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.

-fF    This is equivalent to a gfont F command.

-sn    This is equivalent to a gsize n command.	This option is deprecated.  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.  Nor-
mally 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 adjustment.

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 example,
times is defined as

type "binary" \(mu

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

chartype t text
Unquoted groups of characters are split up into individual characters, 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 accord-
ing 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 characters

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

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 mathematical type-
setting), 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 everything 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
..

Customization
The appearance of equations is controlled by a large number of parameters. 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 hundredths 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
denominator; 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 pro-
duces 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 subscripts 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 normally 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
containing 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  con-
taining 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 parameters 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 parenthesis 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"
Include the contents of file.  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.

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/groff/1.18.1/tmac/eqnrc  Initialization file.

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

Groff Version 1.18.1						  05 October 2001							    EQN(1)`