EQN
Section: User Commands (1)
Updated: 07 February 2013
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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...]
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/sitetmac,
/usr/share/groff/sitetmac,
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 lowresolution, typewriterlike 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 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.
Also, the statement
`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 pointsize 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.
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 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 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 }

(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 predefined using
uaccent
as a tilde accent below the baseline.
 split stexts

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


stexts

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(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
..
 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 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.
This parameter is not used in MathML mode; instead, fat text uses


<mstyle mathvariant='doublestruck'>
 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 subequation 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 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 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 nonzero, 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 nonzero,
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
nth
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 commaseparated
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 sfiles

copy sfiles
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
u+2n


/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.
 *

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
Index
 NAME

 SYNOPSIS

 DESCRIPTION

 OPTIONS

 USAGE

 Controlling delimiters

 Automatic spacing

 New primitives

 Extended primitives

 Customization

 Macros

 Fonts

 FILES

 MATHML MODE LIMITATIONS

 BUGS

 SEE ALSO
