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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 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

eqn  searches  for  the  file  eqnrc  in  the  directories  given  with  the   -M   option   first,   then   in
/usr/lib64/groff/site-tmac,   /usr/share/groff/site-tmac,   and   finally   in  the  standard  macro  directory
/usr/share/groff/1.18.1.4/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 adequately 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.   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 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  men-
tioned 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 char-
acters 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 characters 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 mathematical 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 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 con-
tain 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 hori-
zontal 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  com-
mand.

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 equa-
tion 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 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 opera-
tors.

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 hor-
izontal 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  containing 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  argu-
ment  if  the macro is called with arguments; if there are fewer than n arguments, it will be replaced by noth-
ing.  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; characters 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/1.18.1.4/tmac/eqnrc  Initialization file.

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