EQN(7) BSD Miscellaneous Information Manual EQN(7)NAMEeqn — eqn language reference for mandoc
DESCRIPTION
The eqn language is an equation-formatting 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 Sec‐
ond Edition eqn specification (see SEE ALSO for references).
Equations within mdoc(7) or man(7) documents are enclosed by the stand‐
alone ‘.EQ’ and ‘.EN’ tags. Equations are multi-line 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-sensi‐
tive 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]
White-space 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 avail‐
able: 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 (centre-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 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 delim‐
iter 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. Defi‐
nitions may refer to other definitions; these are evaluated
recursively when text replacement occurs and not when the defini‐
tion is created.
Definitions can create arbitrary strings, for example, the fol‐
lowing is a legal construction.
define foo 'define'
foo bar 'baz'
Self-referencing 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 fol‐
lows:
gfont font
In mandoc, this value is discarded.
gsize Set the default size of subsequent output. Its syntax is as fol‐
lows:
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 state‐
ment is a GNU extension.
undef Unset a previously-defined 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 exten‐
sion.
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 white-space 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 ALSOmandoc(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, 151–157, 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 reimplementa‐
tion 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⟩.
BSD April 18, 2024 BSD
