.\" $Id: eqn.7,v 1.9 2011/07/21 13:18:24 kristaps Exp $ .\" .\" Copyright (c) 2011 Kristaps Dzonsons .\" .\" Permission to use, copy, modify, and distribute this software for any .\" purpose with or without fee is hereby granted, provided that the above .\" copyright notice and this permission notice appear in all copies. .\" .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .\" .Dd $Mdocdate: July 21 2011 $ .Dt EQN 7 .Os .Sh NAME .Nm eqn .Nd eqn language reference for mandoc .Sh DESCRIPTION The .Nm eqn language is a equation-formatting language. It is used within .Xr mdoc 7 and .Xr man 7 .Ux manual pages. This manual describes the subset of the .Nm language accepted by the .Xr mandoc 1 utility. .Pp Equations within .Xr mdoc 7 or .Xr man 7 documents are enclosed by the standalone .Sq \&.EQ and .Sq \&.EN tags. Equations are multi-line blocks consisting of formulas and control statements. .Sh EQUATION STRUCTURE Each equation is bracketed by .Sq \&.EQ and .Sq \&.EN strings. .Em Note : these are not the same as .Xr roff 7 macros, and may only be invoked as .Sq \&.EQ . .Pp The equation grammar is as follows: .Bd -literal -offset indent eqn : box | eqn box box : text | { eqn } | DEFINE text text | SET text text | UNDEF text | box mark text : TEXT mark : DOT | DOTDOT | HAT | TILDE | VEC | DYAD | BAR | UNDER .Ed .Pp Data in TEXT form is a non-empty sequence of non-space characters or a non-empty quoted string. Unless within a quoted string, white-space (and enclosing literal quote pairs) is thrown away. Quoted strings are not scanned for replacement definitions. .Pp The following control statements are available: .Bl -tag -width Ds .It Cm define Replace all occurances of a key with a value. Its syntax is as follows: .Pp .D1 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 define Ar foo 'bar baz' .D1 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 'define' foo bar 'baz' .Ed .Pp Self-referencing definitions will raise an error. .It Cm set Set an equation mode. Both arguments are thrown away. Its syntax is as follows: .Pp .D1 set Ar key val .Pp The .Ar key and .Ar val are not expanded for replacements. .It Cm undef Unset a previously-defined key. Its syntax is as follows: .Pp .D1 define Ar key .Pp Once invoked, the definition for .Ar key is discarded. The .Ar key is not expanded for replacements. .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\*q is interpreted as a literal quote in troff. In mandoc, this is interpreted as a comment. .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 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 kristaps@bsd.lv .