eqn  format equations for troff
eqn [
rvCNR ] [
dxy ]
[
Tname ] [
Mdir ]
[
fF ] [
sn ]
[
pn ] [
mn ]
[
files... ]
It is possible to have whitespace between a command line option and its
parameter.
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/local/lib/groff/sitetmac,
/usr/local/share/groff/sitetmac, and finally in the standard macro
directory
/usr/local/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
lowresolution, typewriterlike devices (although it may work adequately for
very simple input).
 dxy
 Specify delimiters x and y for the left and right end,
respectively, of inline 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 pointsize 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.
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.
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 .ds Su the summation operator
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 example,
times is defined as
 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.
 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 nondisplay 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
 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
predefined using uaccent as a tilde accent below the
baseline.
 split "text"
 This has the same effect as simply
 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
 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 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(0du2n'\
\D'l \\n(0wu2n 0'\D'l 0 \\n(0hu+\\n(0du+2n''\h'\\n(0wu+2n'
.nr 0w +2n
.nr 0d +1n
.nr 0h +1n
..
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,
 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 pointsize 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 subequation 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 subequation 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 nonzero, 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 nonzero, 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 can take arguments. In a macro body,
$n where
n is
between 1 and 9, will be replaced by the
nth 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 commaseparated 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.
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.
 /usr/local/share/groff/1.18.1/tmac/eqnrc
 Initialization file.
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