EQN(7) Miscellaneous Information Manual EQN(7)
NAME
eqn  eqn language reference for mandoc
DESCRIPTION
The eqn language is an equationformatting language. It is used within
mdoc(7) and man(7) UNIX manual pages. It describes the structure of an
equation, not its mathematical meaning. This manual describes the eqn
language accepted by the mandoc(1) utility, which corresponds to the
Second Edition eqn specification (see SEE ALSO for references).
Equations within mdoc(7) or man(7) documents are enclosed by the
standalone `.EQ' and `.EN' tags. Equations are multiline blocks
consisting of formulas and control statements.
EQUATION STRUCTURE
Each equation is bracketed by `.EQ' and `.EN' strings. Note: these are
not the same as roff(7) macros, and may only be invoked as `.EQ'.
The equation grammar is as follows, where quoted strings are case
sensitive literals in the input:
eqn : box  eqn box
box : text
 "{" eqn "}"
 "define" text text
 "ndefine" text text
 "tdefine" text text
 "gfont" text
 "gsize" text
 "set" text text
 "undef" text
 box pos box
 box mark
 "matrix" "{" [col "{" list "}" ]*
 pile "{" list "}"
 font box
 "size" text box
 "left" text eqn ["right" text]
col : "lcol"  "rcol"  "ccol"  "col"
text : [^space\"]+  \".*\"
pile : "lpile"  "cpile"  "rpile"  "pile"
pos : "over"  "sup"  "sub"  "to"  "from"
mark : "dot"  "dotdot"  "hat"  "tilde"  "vec"
 "dyad"  "bar"  "under"
font : "roman"  "italic"  "bold"  "fat"
list : eqn
 list "above" eqn
space : [\^~ \t]
Whitespace consists of the space, tab, circumflex, and tilde characters.
If within a quoted string, these space characters are retained. Quoted
strings are also not scanned for replacement definitions.
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 (centredot), nothing (zerowidth
space), approx (approximately equals), prime (prime), half (onehalf),
partial (partial differential), inf (infinity), >> (much greater), <<
(much less), > (left arrow), < (right arrow), += (plusminus), != (not
equal), == (equivalence), <= (lessthanequal), and >= (morethanequal).
The following control statements are available:
define Replace all occurrences of a key with a value. Its syntax is as
follows:
define key cvalc
The first character of the value string, c, is used as the
delimiter for the value val. This allows for arbitrary enclosure
of terms (not just quotes), such as
define foo 'bar baz'
define foo cbar bazc
It is an error to have an empty key or val. Note that a quoted
key causes errors in some eqn 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.
Definitions can create arbitrary strings, for example, the
following is a legal construction.
define foo 'define'
foo bar 'baz'
Selfreferencing definitions will raise an error. The ndefine
statement is a synonym for define, while tdefine is discarded.
gfont Set the default font of subsequent output. Its syntax is as
follows:
gfont font
In mandoc, this value is discarded.
gsize Set the default size of subsequent output. Its syntax is as
follows:
gsize size
The size value should be an integer.
set Set an equation mode. In mandoc, both arguments are thrown away.
Its syntax is as follows:
set key val
The key and val are not expanded for replacements. This
statement is a GNU extension.
undef Unset a previouslydefined key. Its syntax is as follows:
define key
Once invoked, the definition for key is discarded. The key is
not expanded for replacements. This statement is a GNU
extension.
COMPATIBILITY
This section documents the compatibility of mandoc eqn and the troff eqn
implementation (including GNU troff).
 The text string `\"' is interpreted as a literal quote in troff. In
mandoc, this is interpreted as a comment.
 In troff, The circumflex and tilde whitespace symbols map to fixed
width spaces. In mandoc, these characters are synonyms for the space
character.
 The troff implementation of eqn allows for equation alignment with
the mark and lineup tokens. mandoc discards these tokens. The back
n, fwd n, up n, and down n commands are also ignored.
SEE ALSO
mandoc(1), man(7), mandoc_char(7), mdoc(7), roff(7)
Brian W. Kernighan and Lorinda L. Cherry, "System for Typesetting
Mathematics", Communications of the ACM, 18, 151157, March, 1975.
Brian W. Kernighan and Lorinda L. Cherry, Typesetting Mathematics, User's
Guide, 1976.
Brian W. Kernighan and Lorinda L. Cherry, Typesetting Mathematics, User's
Guide (Second Edition), 1978.
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 mandoc(1) was added in 2011.
AUTHORS
This eqn reference was written by Kristaps Dzonsons, kristaps@bsd.lv.
NetBSD 6.1.5 September 25, 2011 NetBSD 6.1.5
