eqn
format equations for troff or MathML
see also :
groff - troff - pic
Synopsis
eqn
[-rvCNR]
[-d xy]
[-T name]
[-M dir]
[-f F]
[-s n]
[-p n]
[-m n] [files...]
add an example, a script, a trick and tips
examples
no example yet ...
... Feel free to add your own example above to help other Linux-lovers !
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/1.22.1/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.
-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.
files
/usr/share/groff/1.22.1/tmac/eqnrc
Initialization file.
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.
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.
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 ’;
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
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
<mstyle mathsize=’big’>
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
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 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,
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 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.
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 ,
troff , pic , groff_font,
The TeXbook