1EQN(7) BSD Miscellaneous Information Manual EQN(7)
2
4 eqn — eqn language reference for mandoc
5
7 The eqn language is an equation-formatting language. It is used within
8 mdoc(7) and man(7) UNIX manual pages. It describes the structure of an
9 equation, not its mathematical meaning. This manual describes the eqn
10 language accepted by the mandoc(1) utility, which corresponds to the Sec‐
11 ond Edition eqn specification (see SEE ALSO for references).
12 An equation starts with an input line containing exactly the characters
14 ‘.EQ’, may contain multiple input lines, and ends with an input line con‐
15 taining exactly the characters ‘.EN’. Equivalently, an equation can be
16 given in the middle of a single text input line by surrounding it with
17 the equation delimiters defined with the delim statement.
18 The equation grammar is as follows, where quoted strings are case-sensi‐
20 tive literals in the input:
21 eqn : box | eqn box
23 box : text
24 | "{" eqn "}"
25 | "define" text text
26 | "ndefine" text text
27 | "tdefine" text text
28 | "gfont" text
29 | "gsize" text
30 | "set" text text
31 | "undef" text
32 | "sqrt" box
33 | box pos box
34 | box mark
35 | "matrix" "{" [col "{" list "}"]* "}"
36 | pile "{" list "}"
37 | font box
38 | "size" text box
39 | "left" text eqn ["right" text]
40 col : "lcol" | "rcol" | "ccol" | "col"
41 text : [^space\"]+ | \".*\"
42 pile : "lpile" | "cpile" | "rpile" | "pile"
43 pos : "over" | "sup" | "sub" | "to" | "from"
44 mark : "dot" | "dotdot" | "hat" | "tilde" | "vec"
45 | "dyad" | "bar" | "under"
46 font : "roman" | "italic" | "bold" | "fat"
47 list : eqn
48 | list "above" eqn
49 space : [\^~ \t]
50 White-space consists of the space, tab, circumflex, and tilde characters.
52 It is required to delimit tokens consisting of alphabetic characters and
53 it is ignored at other places. Braces and quotes also delimit tokens.
54 If within a quoted string, these space characters are retained. Quoted
55 strings are also not scanned for keywords, glyph names, and expansion of
56 definitions. To print a literal quote character, it can be prepended
57 with a backslash or expressed with the \(dq escape sequence.
58 Subequations can be enclosed in braces to pass them as arguments to oper‐
60 ation keywords, overriding standard operation precedence. Braces can be
61 nested. To set a brace verbatim, it needs to be enclosed in quotes.
62 The following text terms are translated into a rendered glyph, if avail‐
64 able: alpha, beta, chi, delta, epsilon, eta, gamma, iota, kappa, lambda,
65 mu, nu, omega, omicron, phi, pi, psi, rho, sigma, tau, theta, upsilon,
66 xi, zeta, DELTA, GAMMA, LAMBDA, OMEGA, PHI, PI, PSI, SIGMA, THETA, UP‐
67 SILON, XI, inter (intersection), union (union), prod (product), int (in‐
68 tegral), sum (summation), grad (gradient), del (vector differential),
69 times (multiply), cdot (center-dot), nothing (zero-width space), approx
70 (approximately equals), prime (prime), half (one-half), partial (partial
71 differential), inf (infinity), >> (much greater), << (much less), <-
72 (left arrow), -> (right arrow), +- (plus-minus), != (not equal), ==
73 (equivalence), <= (less-than-equal), and >= (more-than-equal). The char‐
74 acter escape sequences documented in mandoc_char(7) can be used, too.
75 The following control statements are available:
77 define Replace all occurrences of a key with a value. Its syntax is as
79 follows:
80 define key cvalc
82 The first character of the value string, c, is used as the delim‐
84 iter for the value val. This allows for arbitrary enclosure of
85 terms (not just quotes), such as
86 define foo 'bar baz'
88 define foo cbar bazc
89 It is an error to have an empty key or val. Note that a quoted
91 key causes errors in some eqn implementations and should not be
92 considered portable. It is not expanded for replacements. Defi‐
93 nitions may refer to other definitions; these are evaluated re‐
94 cursively when text replacement occurs and not when the defini‐
95 tion is created.
96 Definitions can create arbitrary strings, for example, the fol‐
98 lowing is a legal construction.
99 define foo 'define'
101 foo bar 'baz'
102 Self-referencing definitions will raise an error. The ndefine
104 statement is a synonym for define, while tdefine is discarded.
105 delim This statement takes a string argument consisting of two bytes,
107 to be used as the opening and closing delimiters for equations in
108 the middle of text input lines. Conventionally, the dollar sign
109 is used for both delimiters, as follows:
110 .EQ
112 delim $$
113 .EN
114 An equation like $sin pi = 0$ can now be entered
115 in the middle of a text input line.
116 The special statement delim off temporarily disables previously
118 declared delimiters and delim on reenables them.
119 gfont Set the default font of subsequent output. Its syntax is as fol‐
121 lows:
122 gfont font
124 In mandoc, this value is discarded.
126 gsize Set the default size of subsequent output. Its syntax is as fol‐
128 lows:
129 gsize [+|-]size
131 The size value should be an integer. If prepended by a sign, the
133 font size is changed relative to the current size.
134 set Set an equation mode. In mandoc, both arguments are thrown away.
136 Its syntax is as follows:
137 set key val
139 The key and val are not expanded for replacements. This state‐
141 ment is a GNU extension.
142 undef Unset a previously-defined key. Its syntax is as follows:
144 define key
146 Once invoked, the definition for key is discarded. The key is
148 not expanded for replacements. This statement is a GNU exten‐
149 sion.
150 Operation keywords have the following semantics:
152 above See pile.
154 bar Draw a line over the preceding box.
156 bold Set the following box using bold font.
158 ccol Like cpile, but for use in matrix.
160 cpile Like pile, but with slightly increased vertical spacing.
162 dot Set a single dot over the preceding box.
164 dotdot Set two dots (dieresis) over the preceding box.
166 dyad Set a dyad symbol (left-right arrow) over the preceding box.
168 fat A synonym for bold.
170 font Set the second argument using the font specified by the first ar‐
172 gument; currently not recognized by the mandoc(1) eqn parser.
173 from Set the following box below the preceding box, using a slightly
175 smaller font. Used for sums, integrals, limits, and the like.
176 hat Set a hat (circumflex) over the preceding box.
178 italic Set the following box using italic font.
180 lcol Like lpile, but for use in matrix.
182 left Set the first argument as a big left delimiter before the second
184 argument. As an optional third argument, right can follow. In
185 that case, the fourth argument is set as a big right delimiter
186 after the second argument.
187 lpile Like cpile, but subequations are left-justified.
189 matrix Followed by a list of columns enclosed in braces. All columns
191 need to have the same number of subequations. The columns are
192 set as a matrix. The difference compared to multiple subsequent
193 pile operators is that in a matrix, corresponding subequations in
194 all columns line up horizontally, while each pile does vertical
195 spacing independently.
196 over Set a fraction. The preceding box is the numerator, the follow‐
198 ing box is the denominator.
199 pile Followed by a list of subequations enclosed in braces, the sube‐
201 quations being separated by above keywords. Sets the subequa‐
202 tions one above the other, each of them centered. Typically used
203 to represent vectors in coordinate representation.
204 rcol Like rpile, but for use in matrix.
206 right See left; right cannot be used without left. To set a big right
208 delimiter without a big left delimiter, the following construc‐
209 tion can be used:
210 left "" box right delimiter
212 roman Set the following box using the default font.
214 rpile Like cpile, but subequations are right-justified.
216 size Set the second argument with the font size specified by the first
218 argument; currently ignored by mandoc(1). By prepending a plus
219 or minus sign to the first argument, the font size can be se‐
220 lected relative to the current size.
221 sqrt Set the square root of the following box.
223 sub Set the following box as a subscript to the preceding box.
225 sup Set the following box as a superscript to the preceding box. As
227 a special case, if a sup clause immediately follows a sub clause
228 as in
229 mainbox sub subbox sup supbox
231 both are set with respect to the same mainbox, that is, supbox is
233 set above subbox.
234 tilde Set a tilde over the preceding box.
236 to Set the following box above the preceding box, using a slightly
238 smaller font. Used for sums and integrals and the like. As a
239 special case, if a to clause immediately follows a from clause as
240 in
241 mainbox from frombox to tobox
243 both are set below and above the same mainbox.
245 under Underline the preceding box.
247 vec Set a vector symbol (right arrow) over the preceding box.
249 The binary operations from, to, sub, and sup group to the right, that is,
251 mainbox sup supbox sub subbox
253 is the same as
255 mainbox sup {supbox sub subbox}
257 and different from
259 {mainbox sup supbox} sub subbox.
261 By contrast, over groups to the left.
263 In the following list, earlier operations bind more tightly than later
265 operations:
266 1. dyad, vec, under, bar, tilde, hat, dot, dotdot
268 2. fat, roman, italic, bold, size
269 3. sub, sup
270 4. sqrt
271 5. over
272 6. from, to
273
275 This section documents the compatibility of mandoc eqn and the troff eqn
276 implementation (including GNU troff).
277 - The text string ‘\"’ is interpreted as a literal quote in troff. In
279 mandoc, this is interpreted as a comment.
280 - In troff, The circumflex and tilde white-space symbols map to fixed-
281 width spaces. In mandoc, these characters are synonyms for the space
282 character.
283 - The troff implementation of eqn allows for equation alignment with
284 the mark and lineup tokens. mandoc discards these tokens. The back
285 n, fwd n, up n, and down n commands are also ignored.
286
288 mandoc(1), man(7), mandoc_char(7), mdoc(7), roff(7)
289 Brian W. Kernighan and Lorinda L. Cherry, “System for Typesetting
291 Mathematics”, Communications of the ACM, 18, pp. 151–157, March, 1975.
292 Brian W. Kernighan and Lorinda L. Cherry, Typesetting Mathematics, User's
294 Guide, 1976.
295 Brian W. Kernighan and Lorinda L. Cherry, Typesetting Mathematics, User's
297 Guide (Second Edition), 1978.
298
300 The eqn utility, a preprocessor for troff, was originally written by
301 Brian W. Kernighan and Lorinda L. Cherry in 1975. The GNU reimplementa‐
302 tion of eqn, part of the GNU troff package, was released in 1989 by James
303 Clark. The eqn component of mandoc(1) was added in 2011.
304
306 This eqn reference was written by Kristaps Dzonsons <kristaps@bsd.lv>.
307BSD January 10, 2020 BSD