SYNOPSIS eqn [-rvCNR] [-d xy] [-T name] [-M dir] [-f F] [-s n] [-p n] [-m n] [files...] It is possible to have whitespace between a command line option and its parameter. DESCRIPTION This manual page describes the GNU version of eqn, which is part of the groff document formatting system. eqn compiles descriptions of equa- tions embedded within troff input files into commands that are under- stood by troff. Normally, it should be invoked using the -e option of groff. The syntax is quite compatible with Unix eqn. The output of GNU eqn cannot be processed with Unix troff; it must be processed with GNU troff. If no files are given on the command line, the standard input is read. A filename of - causes the standard input to be read. eqn searches for the file eqnrc in the directories given with the -M option first, then in /usr/lib/groff/site-tmac, /usr/share/groff/site- tmac, and finally in the standard macro directory /usr/share/groff/1.21/tmac. If it exists, eqn processes it before the other input files. The -R option prevents this. GNU eqn does not provide the functionality of neqn: it does not support low-resolution, typewriter-like devices (although it may work ade- quately for very simple input). OPTIONS -dxy Specify delimiters x and y for the left and right end, respec- tively, of in-line equations. Any delim statements in the source file overrides this. -C Recognize .EQ and .EN even when followed by a character other than space or newline. -N Don't allow newlines within delimiters. This option allows eqn to recover better from missing closing delimiters. -v Print the version number. -r Only one size reduction. -mn The minimum point-size is n. eqn does not reduce the size of subscripts or superscripts to a smaller size than n. -Tname The output is for device name. Normally, the only effect of this is to define a macro name with a value of 1; eqnrc uses this to provide definitions appropriate for the output device. However, if the specified device is "MathML", the output is MathML markup rather than troff commands, and eqnrc is not loaded at all. The default output device is ps. -Mdir Search dir for eqnrc before the default directories. of the surrounding text. USAGE Only the differences between GNU eqn and Unix eqn are described here. GNU eqn emits Presentation MathML output when invoked with the -T MathML option. GNU eqn sets the input token "..." as three periods or low dots, rather than the three centered dots of classic eqn. To get three cen- tered dots, write cdots or cdot cdot cdot. Most of the new features of the GNU eqn input language are based on TeX. There are some references to the differences between TeX and GNU eqn below; these may safely be ignored if you do not know TeX. Automatic spacing eqn gives each component of an equation a type, and adjusts the spacing between components using that type. Possible types are: ordinary an ordinary character such as `1' or `x'; _ operator a large operator such as `>'; binary a binary operator such as `+'; relation a relation such as `='; opening a opening bracket such as `('; closing a closing bracket such as `)'; punctuation a punctuation character such as `,'; inner a subformula contained within brackets; suppress spacing that suppresses automatic spacing adjust- ment. Components of an equation get a type in one of two ways. type t e This yields an equation component that contains e but that has type t, where t is one of the types mentioned above. For exam- ple, times is defined as type "binary" \(mu The name of the type doesn't have to be quoted, but quoting pro- tects from macro expansion. chartype t text Unquoted groups of characters are split up into individual char- acters, and the type of each character is looked up; this like CSS `large'. In troff output, the point size is increased by 5; in MathML output, the expression uses <mstyle mathsize='big'> e1 smallover e2 This is similar to over; smallover reduces the size of e1 and e2; it also puts less vertical space between e1 or e2 and the fraction bar. The over primitive corresponds to the TeX \over primitive in display styles; smallover corresponds to \over in non-display styles. vcenter e This vertically centers e about the math axis. The math axis is the vertical position about which characters such as `+' and `-' are centered; also it is the vertical position used for the bar of fractions. For example, sum is defined as { type "operator" vcenter size +5 \(*S } (Note that vcenter is silently ignored when generating MathML.) e1 accent e2 This sets e2 as an accent over e1. e2 is assumed to be at the correct height for a lowercase letter; e2 is moved down accord- ing to whether e1 is taller or shorter than a lowercase letter. For example, hat is defined as accent { "^" } dotdot, dot, tilde, vec, and dyad are also defined using the accent primitive. e1 uaccent e2 This sets e2 as an accent under e1. e2 is assumed to be at the correct height for a character without a descender; e2 is moved down if e1 has a descender. utilde is pre-defined using uaccent as a tilde accent below the baseline. split "text" This has the same effect as simply text but text is not subject to macro expansion because it is quoted; text is split up and the spacing between individual characters is adjusted. nosplit text This has the same effect as "text" but because text is not quoted it is subject to macro expansion; ter is treated like opprime. special text e This constructs a new object from e using atroff(1)macro named text. When the macro is called, the string 0s contains the out- put for e, and the number registers 0w, 0h, 0d, 0skern, and 0skew contain the width, height, depth, subscript kern, and skew of e. (The subscript kern of an object says how much a sub- script on that object should be tucked in; the skew of an object says how far to the right of the center of the object an accent over the object should be placed.) The macro must modify 0s so that it outputs the desired result with its origin at the cur- rent point, and increase the current horizontal position by the width of the object. The number registers must also be modified so that they correspond to the result. For example, suppose you wanted a construct that `cancels' an expression by drawing a diagonal line through it. .EQ define cancel 'special Ca' .EN .de Ca . ds 0s \ \Z'\\*(0s'\ \v'\\n(0du'\ \D'l \\n(0wu -\\n(0hu-\\n(0du'\ \v'\\n(0hu' .. Then you could cancel an expression e with cancel { e } Here's a more complicated construct that draws a box round an expression: .EQ define box 'special Bx' .EN .de Bx . ds 0s \ \Z'\h'1n'\\*(0s'\ \Z'\ \v'\\n(0du+1n'\ \D'l \\n(0wu+2n 0'\ \D'l 0 -\\n(0hu-\\n(0du-2n'\ \D'l -\\n(0wu-2n 0'\ \D'l 0 \\n(0hu+\\n(0du+2n'\ '\ \h'\\n(0wu+2n' . nr 0w +2n . nr 0d +1n . nr 0h +1n .. ccol n { ... } lcol n { ... } rcol n { ... } pile n { ... } cpile n { ... } lpile n { ... } rpile n { ... } The integer value n (in hundredths of an em) increases the ver- tical spacing between rows, using groff's \x escape (the value has no effect in MathML mode). Negative values are possible but have no effect. If there is more than a single value given in a matrix, the biggest one is used. Customization When eqn is generating troff markup, the appearance of equations is controlled by a large number of parameters. They have no effect when generating MathML mode, which pushes typesetting and fine motions down- stream to a MathML rendering engine. These parameters can be set using the set command. set p n This sets parameter p to value n; n is an integer. For example, set x_height 45 says that eqn should assume an x height of 0.45 ems. Possible parameters are as follows. Values are in units of hun- dredths of an em unless otherwise stated. These descriptions are intended to be expository rather than definitive. minimum_size eqn doesn't set anything at a smaller point-size than this. The value is in points. fat_offset The fat primitive emboldens an equation by overprinting two copies of the equation horizontally offset by this amount. This parameter is not used in MathML mode; instead, fat text uses <mstyle mathvariant='double-struck'> over_hang A fraction bar is longer by twice this amount than the maximum of the widths of the numerator and denominator; in other words, it overhangs the numerator and denomina- tor by at least this amount. accent_width When bar or under is applied to a single character, the line is this long. Normally, bar or under produces a line whose length is the width of the object to which it applies; in the case of a single character, this tends to the difference of twice the maximum amount by which the sub-equation that the delimiters enclose extends away from the axis and this amount. null_delimiter_space This much horizontal space is inserted on each side of a fraction. script_space The width of subscripts and superscripts is increased by this amount. thin_space This amount of space is automatically inserted after punctuation characters. medium_space This amount of space is automatically inserted on either side of binary operators. thick_space This amount of space is automatically inserted on either side of relations. x_height The height of lowercase letters without ascenders such as `x'. axis_height The height above the baseline of the center of characters such as `+' and `-'. It is important that this value is correct for the font you are using. default_rule_thickness This should set to the thickness of the \(ru character, or the thickness of horizontal lines produced with the \D escape sequence. num1 The over command shifts up the numerator by at least this amount. num2 The smallover command shifts up the numerator by at least this amount. denom1 The over command shifts down the denominator by at least this amount. denom2 The smallover command shifts down the denominator by at least this amount. sup1 Normally superscripts are shifted up by at least this amount. sup2 Superscripts within superscripts or upper limits or sup_drop The baseline of a superscript is no more than this much amount below the top of the object on which the super- script is set. sub_drop The baseline of a subscript is at least this much below the bottom of the object on which the subscript is set. big_op_spacing1 The baseline of an upper limit is at least this much above the top of the object on which the limit is set. big_op_spacing2 The baseline of a lower limit is at least this much below the bottom of the object on which the limit is set. big_op_spacing3 The bottom of an upper limit is at least this much above the top of the object on which the limit is set. big_op_spacing4 The top of a lower limit is at least this much below the bottom of the object on which the limit is set. big_op_spacing5 This much vertical space is added above and below limits. baseline_sep The baselines of the rows in a pile or matrix are nor- mally this far apart. In most cases this should be equal to the sum of num1 and denom1. shift_down The midpoint between the top baseline and the bottom baseline in a matrix or pile is shifted down by this much from the axis. In most cases this should be equal to axis_height. column_sep This much space is added between columns in a matrix. matrix_side_sep This much space is added at each side of a matrix. draw_lines If this is non-zero, lines are drawn using the \D escape sequence, rather than with the \l escape sequence and the \(ru character. body_height The amount by which the height of the equation exceeds this is added as extra space before the line containing A more precise description of the role of many of these parame- ters can be found in Appendix H of The TeXbook. Macros Macros can take arguments. In a macro body, $n where n is between 1 and 9, is replaced by the n-th argument if the macro is called with arguments; if there are fewer than n arguments, it is replaced by noth- ing. A word containing a left parenthesis where the part of the word before the left parenthesis has been defined using the define command is recognized as a macro call with arguments; characters following the left parenthesis up to a matching right parenthesis are treated as comma-separated arguments; commas inside nested parentheses do not ter- minate an argument. sdefine name X anything X This is like the define command, but name is not recognized if called with arguments. include "file" copy "file" Include the contents of file (include and copy are synonyms). Lines of file beginning with .EQ or .EN are ignored. ifdef name X anything X If name has been defined by define (or has been automatically defined because name is the output device) process anything; otherwise ignore anything. X can be any character not appearing in anything. undef name Remove definition of name, making it undefined. Besides the macros mentioned above, the following definitions are available: Alpha, Beta, ..., Omega (this is the same as ALPHA, BETA, ..., OMEGA), ldots (three dots on the base line), and dollar. Fonts eqn normally uses at least two fonts to set an equation: an italic font for letters, and a roman font for everything else. The existing gfont command changes the font that is used as the italic font. By default this is I. The font that is used as the roman font can be changed using the new grfont command. grfont f Set the roman font to f. The italic primitive uses the current italic font set by gfont; the roman primitive uses the current roman font set by grfont. There is also a new gbfont command, which changes the font used by the bold primitive. If you only use the roman, italic and bold primitives to changes fonts within an equation, you can change all the fonts used by your equations just by using gfont, grfont and gbfont commands. MATHML MODE LIMITATIONS MathML is designed on the assumption that it cannot know the exact physical characteristics of the media and devices on which it will be rendered. It does not support fine control of motions and sizes to the same degree troff does. Thus: * eqn parameters have no effect on the generated MathML. * The special, up, down, fwd, and back operations cannot be imple- mented, and yield a MathML `<merror>' message instead. * The vcenter keyword is silently ignored, as centering on the math axis is the MathML default. * Characters that eqn over troff sets extra large - notably the integral sign - may appear too small and need to have their `<mstyle>' wrappers adjusted by hand. As in its troff mode, eqn in MathML mode leaves the .EQ and .EN delim- iters in place for displayed equations, but emits no explicit delim- iters around inline equations. They can, however, be recognized as strings that begin with `<math>' and end with `</math>' and do not cross line boundaries. See the BUGS section for translation limits specific to eqn. BUGS Inline equations are set at the point size that is current at the beginning of the input line. In MathML mode, the mark and lineup features don't work. These could, in theory, be implemented with `<maligngroup>' elements. In MathML mode, each digit of a numeric literal gets a separate `<mn> </mn>' pair, and decimal points are tagged with `<mo></mo>'. This is allowed by the specification, but inefficient. SEE ALSOgroff(1),troff(1),pic(1),groff_font(5), The TeXbook Groff Version 1.21 31 December 2010EQN(1)