NAME
geqn - format equations for troff
SYNOPSIS
geqn [ -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 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/products/src2/gcc/AIX.d/lib/groff/tmac:/usr/lib/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 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.
-R Don't load eqnrc.
-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
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 R;
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 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 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 gtroff(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 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
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 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 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-
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/products/src2/gcc/AIX.d/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.
SEE ALSO
groff(1), gtroff(1), groff_font(5), The TEXbook