Provided by: groff-base_1.21-7_i386

#### NAME

       eqn - format equations for troff or MathML



#### SYNOPSIS

       eqn [-rvCNR] [-d xy] [-T name] [-M dir] [-f F] [-s n] [-p n] [-m n]
[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 is read.  A filename of - causes 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/1.21/tmac.  If it exists, eqn processes 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



#### 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 does not reduce the size of
subscripts or superscripts to a smaller size than n.

-Tname The output is for device name.  Normally,  the  only  effect  of
this  is  to  define  a macro name with a value of 1; eqnrc uses
this to provide definitions appropriate for the  output  device.
However,  if  the  specified  device  is “MathML”, the output is
MathML markup rather than  troff  commands,  and  eqnrc  is  not
loaded at all.  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 normally sets 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 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.

GNU  eqn  emits  Presentation  MathML  output  when  invoked  with  the
-T MathML option.

GNU  eqn  sets  the  input  token  "..."  as three periods or low dots,
rather than the three centered dots  of  classic  eqn.   To  get  three
centered dots, write cdots or cdot cdot cdot.

Most  of  the  new  features of the GNU eqn input language 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 Σ';

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
big e  Enlarges the expression it modifies; intended to have  semantics
like  CSS large'.  In troff output, the point size is increased
by 5; in MathML output, the expression uses

<mstyle mathsize='big'>

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 }

(Note that vcenter is silently ignored when generating MathML.)

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  is  moved  down
according  to  whether  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 is  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  is  split up and the spacing between individual characters

nosplit text
This has the same effect as

"text"

but because text is not quoted it is subject to macro expansion;
text  is  not  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 is tucked under the prime as
a  subscript  to  the  A  (as  is  conventional  in mathematical
typesetting), whereas with prime the 1 is  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 is 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 contains the
output for e, and the number registers 0w, 0h, 0d,  0skern,  and
0skew 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 outputs 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
picture.

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
vertical  spacing  between  rows,  using  groff's \x escape (the
value has no  effect  in  MathML  mode).   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
When eqn is generating troff markup, the  appearance  of  equations  is
controlled  by  a large number of parameters.  They have no effect when
generating MathML mode,  which  pushes  typesetting  and  fine  motions
downstream  to  a MathML rendering engine.  These parameters 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 doesn't 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.   This  parameter  is  not  used  in MathML mode;

<mstyle mathvariant='double-struck'>

over_hang
A fraction bar is longer by twice this  amount  than  the
maximum  of  the widths of the numerator and denominator;
in  other  words,  it   overhangs   the   numerator   and
denominator by at least this amount.

accent_width
When  bar  or under is applied to a single character, the
line is 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 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 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 shifts up the numerator by at least this
amount.

num2   The smallover command shifts up the numerator by at least
this amount.

denom1 The  over command shifts down the denominator by at least
this amount.

denom2 The smallover command shifts down the denominator  by  at
least this amount.

sup1   Normally  superscripts  are  shifted  up by at least this
amount.

sup2   Superscripts  within  superscripts  or  upper  limits  or
numerators  of  smallover  fractions are 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  are shifted up by at least
this amount.  This is usually less than sup2.

sub1   Subscripts are normally shifted down  by  at  least  this
amount.

sub2   When  there  is  both  a subscript and a superscript, the
subscript is shifted down by at least this amount.

sup_drop
The baseline of a superscript is 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 is 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 is 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 is 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 is 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 is at least this much below  the
bottom of the object on which the limit is set.

big_op_spacing5
This much vertical space is added above and below limits.

baseline_sep
The  baselines  of  the  rows  in  a  pile  or matrix are
normally 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 is shifted down by this much
from  the  axis.   In  most cases this should be equal to
axis_height.

column_sep
This much space is added between columns in a matrix.

matrix_side_sep
This much space is added at each side of a matrix.

draw_lines
If this is non-zero, lines are 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  is  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  is  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 behaves like define and
tdefine is ignored, otherwise tdefine behaves like define
and ndefine is 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, is replaced by the n-th argument if the  macro  is  called  with
arguments;  if  there  are  fewer  than  n arguments, it is 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 is recognized  as  a  macro  call  with  arguments;  characters
following  the  left parenthesis up to a matching right parenthesis are
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 is not 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 are 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 causes a character to be set in italic type.  A type of digit
causes a character to be set in roman type.



#### INTERACTIONWITHTBL

       It is not advisable to use the hash character (#) as  a  delimiter  for
in-line  equations in eqn since tbl(1) uses a macro called .T#, causing
a clash.



#### FILES

       /usr/share/groff/1.21/tmac/eqnrc  Initialization file.



#### MATHMLMODELIMITATIONS

       MathML is designed on the assumption that  it  cannot  know  the  exact
physical  characteristics  of the media and devices on which it will be
rendered.  It does not support fine control of motions and sizes to the
same degree troff does.  Thus:

*      eqn parameters have no effect on the generated MathML.

*      The  special,  up,  down,  fwd,  and  back  operations cannot be
implemented, and yield a MathML <merror>' message instead.

*      The vcenter keyword is silently ignored,  as  centering  on  the
math axis is the MathML default.

*      Characters  that  eqn  over troff sets extra large – notably the
integral sign – may appear too small  and  need  to  have  their
<mstyle>' wrappers adjusted by hand.

As  in  its  troff  mode,  eqn  in  MathML  mode leaves the .EQ and .EN
delimiters in place for displayed  equations,  but  emits  no  explicit
delimiters  around  inline equations.  They can, however, be recognized
as strings that begin with $' and end with $' and  do  not
cross line boundaries.

See the BUGS section for translation limits specific to eqn.



#### BUGS

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

In MathML mode, the mark and lineup features don't work.  These  could,
in theory, be implemented with <maligngroup>' elements.

In  MathML  mode, each digit of a numeric literal gets a separate <mn>
</mn>' pair, and decimal points are tagged with <mo></mo>'.   This  is
allowed by the specification, but inefficient.



#### SEEALSO

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