eqn man page on OpenDarwin

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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	 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/lib/groff/site-tmac,	/usr/share/groff/site-
tmac,	 and	finally	   in	 the	standard    macro    directory
/usr/share/groff/1.18.1/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 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 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 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
..

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	 exam‐
ple,

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	 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 maxi‐
mum 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 cor‐
rect 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 lim‐
its 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	 typi‐
cally 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"
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/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), groff_font(5), The TeXbook

Groff Version 1.18.1		   Nov	2003				EQN(1)
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