NAME¶
eqn - format equations for troff or MathML
SYNOPSIS¶
[
-rvCNR] [
-d
xy] [
-T name]
[
-M dir] [
-f
F] [
-s n]
[
-p n] [
-m
n] [
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 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
/usr/lib/groff/site-tmac,
/usr/share/groff/site-tmac, and finally in the standard macro directory
/usr/share/groff/1.21/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¶
- -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.
- -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 surrounding text.
USAGE¶
Only the differences between GNU
eqn and Unix eqn are described here.
GNU
eqn emits Presentation MathML output when invoked with the
-T MathML option.
GNU eqn sets the input token
"..." as three periods or low
dots, rather than the three centered dots of classic eqn. To get three
centered dots, write
cdots or
cdot cdot cdot.
Most of the new features of the GNU
eqn input language 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 .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.
New primitives¶
- big e
- Enlarges the expression it modifies; intended to have
semantics like CSS `large'. In troff output, the point size is increased
by 5; in MathML output, the expression uses
- 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
}
- (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
- 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
- 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
- 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 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
..
- space n
- A positive value of the integer n (in
hundredths of an em) sets the vertical spacing before the equation, a
negative value sets the spacing after the equation, replacing the default
values. This primitive 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 parameters. 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,
- 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 doesn't 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. This parameter is not used in MathML mode; instead, fat text
uses
-
<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.
- denom2
- The smallover command shifts down the denominator by
at least this amount.
- sup1
- Normally superscripts are shifted up by at least this
amount.
- sup2
- Superscripts within superscripts or upper limits or
numerators of smallover fractions are 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 are shifted up by at least this amount. This is
usually less than sup2.
- sub1
- Subscripts are normally shifted down 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
- The amount by which the depth of the equation exceeds this
is 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 behaves like
define and tdefine is ignored, otherwise tdefine
behaves like define and ndefine is 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, is replaced by the
n-th argument 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.
INTERACTION WITH TBL¶
It is not advisable to use the hash character (#) as a delimiter for in-line
equations in
eqn since
tbl(1) uses a macro called
.T#,
causing a clash.
FILES¶
- /usr/share/groff/1.21/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.
- *
- The vcenter keyword is silently ignored, as
centering on the math axis is the MathML default.
- *
- Characters that eqn over troff sets extra large
– notably the integral sign – may appear too small and need to
have their `<mstyle>' wrappers adjusted by hand.
As in its troff mode,
eqn in MathML mode leaves the
.EQ and
.EN delimiters in place for displayed equations, but emits no explicit
delimiters around inline equations. They can, however, be recognized as
strings that begin with `<math>' and end with `</math>' and do not
cross line boundaries.
See the
BUGS section for translation limits specific to
eqn.
BUGS¶
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