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EQN(7)                 Miscellaneous Information Manual                 EQN(7)

NAME
     eqn -- 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
     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 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-
     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]

     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
     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 (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
             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'

             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
             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 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
             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 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 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, 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
     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