EQN(1) General Commands Manual EQN(1)
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...]
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 to
be read.
eqn searches for the file eqnrc in the directories given with the -M option first, then in /etc/groff/site-
tmac, /etc/groff/site-tmac, and finally in the standard macro directory /usr/share/groff/1.22.2/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 adequately for very simple input).
OPTIONS
It is possible to have whitespace between a command line option and its parameter.
-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. Also, the state‐
ment `delim on' is not handled specially.
-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.
-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 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 sur‐
Controlling delimiters
If not in compatibility mode, eqn recognizes
delim on
to restore the delimiters which have been previously disabled with a call to `delim off'. If delimiters
haven't been specified, the call has no effect.
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 men‐
tioned 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 equa‐
tion. 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
tions. 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 is adjusted.
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 characters is not 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 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 corre‐
spond to the result.
..
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 equa‐
tion, a negative value sets the spacing after the equation, replacing the default values. This primi‐
tive 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 parame‐
ters. 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
<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.
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
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.
FILES
/usr/share/groff/1.22.2/tmac/eqnrc Initialization file.
MATHML MODE LIMITATIONS
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.
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.
SEE ALSO
groff(1), troff(1), pic(1), groff_font(5), The TeXbook
Groff Version 1.22.2 7 February 2013 EQN(1)
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