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# OpenDarwin 7.2.1 - man page for eqn (opendarwin section 1)

EQN(1)				     General Commands Manual				   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 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 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 adequately for very simple input).

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  new-
line.

-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  super-
scripts 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	appropri-
ate 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 nor-
mally 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 sur-
rounding 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 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 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 char-
acter; 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 corre-
sponds 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 posi-
tion 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 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 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 regis-
ters  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 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 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 punc-
tuation 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  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 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 numera-
tors  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 sub-
script 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 super-
script 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 lim-
its.

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 base-
line 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 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, 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  argu-
ments; 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  primi-
tives to changes fonts within an equation, you can change all the fonts used by your equa-
tions 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 Version 1.18.1			    Nov  2003					   EQN(1)`