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## EQN(1)

### Contents




### NAME[Toc][Back]

       eqn - format equations for troff


### SYNOPSIS[Toc][Back]

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

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


### DESCRIPTION[Toc][Back]

       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 to be read.

eqn  searches  for  the  file   eqnrc   using   the   path
/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 adequately for very simple input).


### OPTIONS[Toc][Back]

       -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[Toc][Back]

       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    [Toc]    [Back]
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

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    [Toc]    [Back]
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 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

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  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  can-
cel { 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    [Toc]    [Back]
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 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  subequation
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
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
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
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
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    [Toc]    [Back]
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; 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 any-
thing.  X can be any  character  not  appearing  in
anything.

Fonts    [Toc]    [Back]
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[Toc][Back]

       /usr/share/tmac/eqnrc  Initialization file.


### BUGS[Toc][Back]

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


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