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

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.

-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-

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.

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

Groff Version 1.19.2            6 February 2006                         EQN(1)
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