\"      Id: eqn.7,v 1.39 2020/01/10 11:55:04 schwarze Exp
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\" Copyright (c) 2014 Ingo Schwarze <[email protected]>
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Dd January 10, 2020
Dt EQN 7
Os
Sh NAME
Nm eqn
Nd eqn language reference for mandoc
Sh DESCRIPTION
The
Nm eqn
language is an equation-formatting language.
It is used within
Xr mdoc 7
and
Xr man 7
Ux
manual pages.
It describes the
Em structure
of an equation, not its mathematical meaning.
This manual describes the
Nm
language accepted by the
Xr mandoc 1
utility, which corresponds to the Second Edition
Nm
specification (see
Sx SEE ALSO
for references).
Pp
An equation starts with an input line containing exactly the characters
Sq \&.EQ ,
may contain multiple input lines, and ends with an input line
containing exactly the characters
Sq \&.EN .
Equivalently, an equation can be given in the middle of a single
text input line by surrounding it with the equation delimiters
defined with the
Cm delim
statement.
Pp
The equation grammar is as follows, where quoted strings are
case-sensitive literals in the input:
Bd -literal -offset indent
eqn     : box | eqn box
box     : text
       | \(dq{\(dq eqn \(dq}\(dq
       | \(dqdefine\(dq text text
       | \(dqndefine\(dq text text
       | \(dqtdefine\(dq text text
       | \(dqgfont\(dq text
       | \(dqgsize\(dq text
       | \(dqset\(dq text text
       | \(dqundef\(dq text
       | \(dqsqrt\(dq box
       | box pos box
       | box mark
       | \(dqmatrix\(dq \(dq{\(dq [col \(dq{\(dq list \(dq}\(dq]* \(dq}\(dq
       | pile \(dq{\(dq list \(dq}\(dq
       | font box
       | \(dqsize\(dq text box
       | \(dqleft\(dq text eqn [\(dqright\(dq text]
col     : \(dqlcol\(dq | \(dqrcol\(dq | \(dqccol\(dq | \(dqcol\(dq
text    : [^space\e\(dq]+ | \e\(dq.*\e\(dq
pile    : \(dqlpile\(dq | \(dqcpile\(dq | \(dqrpile\(dq | \(dqpile\(dq
pos     : \(dqover\(dq | \(dqsup\(dq | \(dqsub\(dq | \(dqto\(dq | \(dqfrom\(dq
mark    : \(dqdot\(dq | \(dqdotdot\(dq | \(dqhat\(dq | \(dqtilde\(dq | \(dqvec\(dq
       | \(dqdyad\(dq | \(dqbar\(dq | \(dqunder\(dq
font    : \(dqroman\(dq | \(dqitalic\(dq | \(dqbold\(dq | \(dqfat\(dq
list    : eqn
       | list \(dqabove\(dq eqn
space   : [\e^~ \et]
Ed
Pp
White-space consists of the space, tab, circumflex, and tilde
characters.
It is required to delimit tokens consisting of alphabetic characters
and it is ignored at other places.
Braces and quotes also delimit tokens.
If within a quoted string, these space characters are retained.
Quoted strings are also not scanned for keywords, glyph names,
and expansion of definitions.
To print a literal quote character, it can be prepended with a
backslash or expressed with the \e(dq escape sequence.
Pp
Subequations can be enclosed in braces to pass them as arguments
to operation keywords, overriding standard operation precedence.
Braces can be nested.
To set a brace verbatim, it needs to be enclosed in quotes.
Pp
The following text terms are translated into a rendered glyph, if
available: alpha, beta, chi, delta, epsilon, eta, gamma, iota, kappa,
lambda, mu, nu, omega, omicron, phi, pi, psi, rho, sigma, tau, theta,
upsilon, xi, zeta, DELTA, GAMMA, LAMBDA, OMEGA, PHI, PI, PSI, SIGMA,
THETA, UPSILON, XI, inter (intersection), union (union), prod (product),
int (integral), sum (summation), grad (gradient), del (vector
differential), times (multiply), cdot (center-dot), nothing (zero-width
space), approx (approximately equals), prime (prime), half (one-half),
partial (partial differential), inf (infinity), >> (much greater), <<
(much less), <\- (left arrow), \-> (right arrow), +\- (plus-minus), !=
(not equal), == (equivalence), <= (less-than-equal), and >=
(more-than-equal).
The character escape sequences documented in
Xr mandoc_char 7
can be used, too.
Pp
The following control statements are available:
Bl -tag -width Ds
It Cm define
Replace all occurrences of a key with a value.
Its syntax is as follows:
Pp
D1 Cm define Ar key cvalc
Pp
The first character of the value string,
Ar c ,
is used as the delimiter for the value
Ar val .
This allows for arbitrary enclosure of terms (not just quotes), such as
Pp
D1 Cm define Ar foo \(aqbar baz\(aq
D1 Cm define Ar foo cbar bazc
Pp
It is an error to have an empty
Ar key
or
Ar val .
Note that a quoted
Ar key
causes errors in some
Nm
implementations and should not be considered portable.
It is not expanded for replacements.
Definitions may refer to other definitions; these are evaluated
recursively when text replacement occurs and not when the definition is
created.
Pp
Definitions can create arbitrary strings, for example, the following is
a legal construction.
Bd -literal -offset indent
define foo \(aqdefine\(aq
foo bar \(aqbaz\(aq
Ed
Pp
Self-referencing definitions will raise an error.
The
Cm ndefine
statement is a synonym for
Cm define ,
while
Cm tdefine
is discarded.
It Cm delim
This statement takes a string argument consisting of two bytes,
to be used as the opening and closing delimiters for equations
in the middle of text input lines.
Conventionally, the dollar sign is used for both delimiters,
as follows:
Bd -literal -offset indent
\&.EQ
delim $$
\&.EN
An equation like $sin pi = 0$ can now be entered
in the middle of a text input line.
Ed
Pp
The special statement
Cm delim off
temporarily disables previously declared delimiters and
Cm delim on
reenables them.
It Cm gfont
Set the default font of subsequent output.
Its syntax is as follows:
Pp
D1 Cm gfont Ar font
Pp
In mandoc, this value is discarded.
It Cm gsize
Set the default size of subsequent output.
Its syntax is as follows:
Pp
D1 Cm gsize Oo +|\- Oc Ns Ar size
Pp
The
Ar size
value should be an integer.
If prepended by a sign,
the font size is changed relative to the current size.
It Cm set
Set an equation mode.
In mandoc, both arguments are thrown away.
Its syntax is as follows:
Pp
D1 Cm set Ar key val
Pp
The
Ar key
and
Ar val
are not expanded for replacements.
This statement is a GNU extension.
It Cm undef
Unset a previously-defined key.
Its syntax is as follows:
Pp
D1 Cm define Ar key
Pp
Once invoked, the definition for
Ar key
is discarded.
The
Ar key
is not expanded for replacements.
This statement is a GNU extension.
El
Pp
Operation keywords have the following semantics:
Bl -tag -width Ds
It Cm above
See
Cm pile .
It Cm bar
Draw a line over the preceding box.
It Cm bold
Set the following box using bold font.
It Cm ccol
Like
Cm cpile ,
but for use in
Cm matrix .
It Cm cpile
Like
Cm pile ,
but with slightly increased vertical spacing.
It Cm dot
Set a single dot over the preceding box.
It Cm dotdot
Set two dots (dieresis) over the preceding box.
It Cm dyad
Set a dyad symbol (left-right arrow) over the preceding box.
It Cm fat
A synonym for
Cm bold .
It Cm font
Set the second argument using the font specified by the first argument;
currently not recognized by the
Xr mandoc 1
Nm
parser.
It Cm from
Set the following box below the preceding box,
using a slightly smaller font.
Used for sums, integrals, limits, and the like.
It Cm hat
Set a hat (circumflex) over the preceding box.
It Cm italic
Set the following box using italic font.
It Cm lcol
Like
Cm lpile ,
but for use in
Cm matrix .
It Cm left
Set the first argument as a big left delimiter before the second argument.
As an optional third argument,
Cm right
can follow.
In that case, the fourth argument is set as a big right delimiter after
the second argument.
It Cm lpile
Like
Cm cpile ,
but subequations are left-justified.
It Cm matrix
Followed by a list of columns enclosed in braces.
All columns need to have the same number of subequations.
The columns are set as a matrix.
The difference compared to multiple subsequent
Cm pile
operators is that in a
Cm matrix ,
corresponding subequations in all columns line up horizontally,
while each
Cm pile
does vertical spacing independently.
It Cm over
Set a fraction.
The preceding box is the numerator, the following box is the denominator.
It Cm pile
Followed by a list of subequations enclosed in braces,
the subequations being separated by
Cm above
keywords.
Sets the subequations one above the other, each of them centered.
Typically used to represent vectors in coordinate representation.
It Cm rcol
Like
Cm rpile ,
but for use in
Cm matrix .
It Cm right
See
Cm left ;
Cm right
cannot be used without
Cm left .
To set a big right delimiter without a big left delimiter, the following
construction can be used:
Pp
D1 Cm left No \(dq\(dq Ar box Cm right Ar delimiter
It Cm roman
Set the following box using the default font.
It Cm rpile
Like
Cm cpile ,
but subequations are right-justified.
It Cm size
Set the second argument with the font size specified by the first
argument; currently ignored by
Xr mandoc 1 .
By prepending a plus or minus sign to the first argument,
the font size can be selected relative to the current size.
It Cm sqrt
Set the square root of the following box.
It Cm sub
Set the following box as a subscript to the preceding box.
It Cm sup
Set the following box as a superscript to the preceding box.
As a special case, if a
Cm sup
clause immediately follows a
Cm sub
clause as in
Pp
D1 Ar mainbox Cm sub Ar subbox Cm sup Ar supbox
Pp
both are set with respect to the same
Ar mainbox ,
that is,
Ar supbox
is set above
Ar subbox .
It Cm tilde
Set a tilde over the preceding box.
It Cm to
Set the following box above the preceding box,
using a slightly smaller font.
Used for sums and integrals and the like.
As a special case, if a
Cm to
clause immediately follows a
Cm from
clause as in
Pp
D1 Ar mainbox Cm from Ar frombox Cm to Ar tobox
Pp
both are set below and above the same
Ar mainbox .
It Cm under
Underline the preceding box.
It Cm vec
Set a vector symbol (right arrow) over the preceding box.
El
Pp
The binary operations
Cm from ,
Cm to ,
Cm sub ,
and
Cm sup
group to the right, that is,
Pp
D1 Ar mainbox Cm sup Ar supbox Cm sub Ar subbox
Pp
is the same as
Pp
D1 Ar mainbox Cm sup Brq Ar supbox Cm sub Ar subbox
Pp
and different from
Pp
D1 Bro Ar mainbox Cm sup Ar supbox Brc Cm sub Ar subbox .
Pp
By contrast,
Cm over
groups to the left.
Pp
In the following list, earlier operations bind more tightly than
later operations:
Pp
Bl -enum -compact
It
Cm dyad ,
Cm vec ,
Cm under ,
Cm bar ,
Cm tilde ,
Cm hat ,
Cm dot ,
Cm dotdot
It
Cm fat ,
Cm roman ,
Cm italic ,
Cm bold ,
Cm size
It
Cm sub ,
Cm sup
It
Cm sqrt
It
Cm over
It
Cm from ,
Cm to
El
Sh COMPATIBILITY
This section documents the compatibility of mandoc
Nm
and the troff
Nm
implementation (including GNU troff).
Pp
Bl -dash -compact
It
The text string
Sq \e\(dq
is interpreted as a literal quote in troff.
In mandoc, this is interpreted as a comment.
It
In troff, The circumflex and tilde white-space symbols map to
fixed-width spaces.
In mandoc, these characters are synonyms for the space character.
It
The troff implementation of
Nm
allows for equation alignment with the
Cm mark
and
Cm lineup
tokens.
mandoc discards these tokens.
The
Cm back Ar n ,
Cm fwd Ar n ,
Cm up Ar n ,
and
Cm down Ar n
commands are also ignored.
El
Sh SEE ALSO
Xr mandoc 1 ,
Xr man 7 ,
Xr mandoc_char 7 ,
Xr mdoc 7 ,
Xr roff 7
Rs
%A Brian W. Kernighan
%A Lorinda L. Cherry
%T System for Typesetting Mathematics
%J Communications of the ACM
%V 18
%P pp. 151\(en157
%D March, 1975
Re
Rs
%A Brian W. Kernighan
%A Lorinda L. Cherry
%T Typesetting Mathematics, User's Guide
%D 1976
Re
Rs
%A Brian W. Kernighan
%A Lorinda L. Cherry
%T Typesetting Mathematics, User's Guide (Second Edition)
%D 1978
Re
Sh HISTORY
The eqn utility, a preprocessor for troff, was originally written by
Brian W. Kernighan and Lorinda L. Cherry in 1975.
The GNU reimplementation of eqn, part of the GNU troff package, was
released in 1989 by James Clark.
The eqn component of
Xr mandoc 1
was added in 2011.
Sh AUTHORS
This
Nm
reference was written by
An Kristaps Dzonsons Aq Mt [email protected] .

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