EQN(1)                                                     EQN(1)

NAME
eqn - format equations for troff

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

DESCRIPTION
This manual page describes the GNU version of  eqn,  which
is part of the groff document formatting system.  eqn com-
piles 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/lib/groff/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
-C     Recognize .EQ and .EN even when followed by a char-
acter 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 defini-
tions  appropriate  for  the  output  device.   The
default output device is ps.

-Mdir  Search  dir  for  eqnrc before the default directo-
ries.

-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 equa-
tions 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 the summation opera-
tor;

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 charac-
ter is looked up; this changes  the  type  that  is
stored for each character; it says that the charac-
ters in text from now on have type t.  For example,

chartype "punctuation" .,;:

would  make  the characters .,;: have type punctua-
tion 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 frac-
tions.  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  typeset-
ting), 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,  sub-
script 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 num-
ber 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 charac-
ter, 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  pro-
duced  with  the  left  and
right primitives will  have
a combined height and depth
of at least this many thou-
sandths  of twice the maxi-
mum  amount  by  which  the
sub-equation    that    the
delimiters enclose  extends
away from the axis.

delimiter_shortfall     Extensible  delimiters pro-
duced  with  the  left  and
right  primitives will have
a combined height and depth
not  less  than the differ-
ence of twice  the  maximum
amount  by  which  the sub-
equation  that  the  delim-
iters  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  charac-
ters.

medium_space            This  amount  of  space  is
automatically  inserted  on
either side of binary oper-
ators.

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 base-
line of the center of char-
acters 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 char-
acter, 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 super-
scripts 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 denomi-
nators 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  sub-
script  and  a superscript,
the   subscript   will   be
shifted  down  by  at least
this amount.

sup_drop                The baseline  of  a  super-
script 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 sub-
script 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 char-
acter.

body_height             The  amount  by  which  the
height   of   the  equation
as  extra  space before the
line containing  the  equa-
tion   (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  equa-
tion   (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   and   latin1
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; characters following the left parenthesis up to
a matching right parenthesis will be treated as comma-sep-
arated  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 begin-
ning 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
eqn normally uses at least two fonts to set  an  equation:
an  italic  font  for letters, and a roman font for every-
thing 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 com-
mands.

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

FILES
/usr/lib/groff/tmac/eqnrc  Initialization file.

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

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