EQN(1)                                                                  EQN(1)



NAME
       eqn - format equations for troff

SYNOPSIS
       eqn [-rvCNR] [-dcc] [-Tname] [-Mdir] [-fF] [-sn] [-pn] [-mn] [files...]

DESCRIPTION
       This manual page describes the GNU version of eqn, which is part of the
       groff document formatting system.  eqn compiles descriptions of
       equations embedded within troff input files into commands that are
       understood 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 will be read.  A filename of - will cause the standard input to
       be read.

       eqn searches for the file eqnrc using the path .:/usr/local/share/tmac.
       If it exists, eqn will process 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
       adequately for very simple input).

OPTIONS
       -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 will not reduce the size of
              subscripts or superscripts to a smaller size than n.

       -Tname The output is for device name. The only effect of this is to
              define a macro name with a value of 1. Typically eqnrc will use
              this to provide definitions appropriate for the output device.
              The default output device is ps.

       -Mdir  Search dir for eqnrc before the default directories.

       -R     Don't load eqnrc.

       -fF    This is equivalent to a gfont F command.

       -sn    This is equivalent to a gsize n command.  This option is
              deprecated.  eqn will normally set equations at whatever the
              current point size is when the equation is encountered.

       -pn    This says that subscripts and superscripts should be n points
              smaller than the surrounding text.  This option is deprecated.
              Normally eqn makes sets subscripts and superscripts at 70% of
              the size of the surrounding text.

USAGE
       Only the differences between GNU eqn and Unix eqn are described here.

       Most of the new features of GNU eqn 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 adjustment.

       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
              example, times is defined as

                     type "binary" \(mu


              The name of the type doesn't have to be quoted, but quoting
              protects from macro expansion.

       chartype t text
              Unquoted groups of characters are split up into individual
              characters, and the type of each character is looked up; this
              changes the type that is stored for each character; it says that
              the characters in text from now on have type t. For example,

                     chartype "punctuation" .,;:


              would make the characters .,;: have type punctuation whenever
              they subsequently appeared in an equation.  The type t can also
              be letter or digit; in these cases chartype changes the font
              type of the characters.  See the Fonts subsection.

   New primitives
       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 }

       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 will be moved down
              according if 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 will be
              moved down if e1 has a descender.  utilde is pre-defined using
              uaccent as a tilde accent below the baseline.

       split stexts
              This has the same effect as simply

                     text


              but text is not subject to macro expansion because it is quoted;
              text will be split up and the spacing between individual
              characters will be adjusted.

       nosplit text
              This has the same effect as

                     stexts


              but because text is not quoted it will be subject to macro
              expansion; text will not be split up and the spacing between
              individual characters will not be adjusted.

       e opprime
              This is a variant of prime that acts as an operator on e. It
              produces a different result from prime in a case such as
              A opprime sub 1: with opprime the 1 will be tucked under the
              prime as a subscript to the A (as is conventional in
              mathematical typesetting), whereas with prime the 1 will be a
              subscript to the prime character.  The precedence of opprime is
              the same as that of bar and under, which is higher than that of
              everything except accent and uaccent. In unquoted text a ' that
              is not the first character will be treated like opprime.

       special text e
              This constructs a new object from e using a troff(1) macro named
              text. When the macro is called, the string 0s will contain the
              output for e, and the number registers 0w, 0h, 0d, 0skern and
              0skew will contain the width, height, depth, subscript kern, and
              skew of e. (The subscript kern of an object says how much a
              subscript 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 will output the desired result with its origin at
              the current 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
                     ..

   Customization
       The appearance of equations is controlled by a large number of
       parameters. These 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
              hundredths of an em unless otherwise stated.  These descriptions
              are intended to be expository rather than definitive.

              minimum_size
                     eqn will not 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.

              over_hang
                     A fraction bar will be longer by twice this amount than
                     the maximum of the widths of the numerator and
                     denominator; in other words, it will overhang the
                     numerator and denominator by at least this amount.

              accent_width
                     When bar or under is applied to a single character, the
                     line will be 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 produce a line that looks too long.

              delimiter_factor
                     Extensible delimiters produced with the left and right
                     primitives will have a combined height and depth of at
                     least this many thousandths of twice the maximum amount
                     by which the sub-equation that the delimiters enclose
                     extends away from the axis.

              delimiter_shortfall
                     Extensible delimiters produced with the left and right
                     primitives will have a combined height and depth not less
                     than 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 will shift up the numerator by at least
                     this amount.

              num2   The smallover command will shift up the numerator by at
                     least this amount.

              denom1 The over command will shift down the denominator by at
                     least this amount.

              denom2 The smallover command will shift down the denominator by
                     at least this amount.

              sup1   Normally superscripts will be shifted up by at least this
                     amount.

              sup2   Superscripts within superscripts or upper limits or
                     numerators of smallover fractions will be shifted up by
                     at least this amount.  This is usually less than sup1.

              sup3   Superscripts within denominators or square roots or
                     subscripts or lower limits will be shifted up by at least
                     this amount.  This is usually less than sup2.

              sub1   Subscripts will normally be shifted down by at least this
                     amount.

              sub2   When there is both a subscript and a superscript, the
                     subscript will be shifted down by at least this amount.

              sup_drop
                     The baseline of a superscript will be no more than this
                     much amount below the top of the object on which the
                     superscript is set.

              sub_drop
                     The baseline of a subscript will be 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 will be 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 will be 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 will be 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 will be at least this much below
                     the bottom of the object on which the limit is set.

              big_op_spacing5
                     This much vertical space will be added above and below
                     limits.

              baseline_sep
                     The baselines of the rows in a pile or matrix will
                     normally be 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 will be shifted down by this
                     much from the axis.  In most cases this should be equal
                     to axis_height.

              column_sep
                     This much space will be added between columns in a
                     matrix.

              matrix_side_sep
                     This much space will be added at each side of a matrix.

              draw_lines
                     If this is non-zero, lines will be 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 will be added as extra space before the line
                     containing the equation (using \x.) The default value is
                     85.

              body_depth
                     The amount by which the depth of the equation exceeds
                     this will be added as extra space after the line
                     containing the equation (using \x.) The default value is
                     35.

              nroff  If this is non-zero, then ndefine will behave like define
                     and tdefine will be ignored, otherwise tdefine will
                     behave like define and ndefine will be ignored.  The
                     default value is 0 (This is typically changed to 1 by the
                     eqnrc file for the ascii and latin1 devices.)

              A more precise description of the role of many of these
              parameters 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, will be replaced by the n-th argument if the macro is called
       with arguments; if there are fewer than n arguments, it will be
       replaced by nothing.  A word containing a left parenthesis where the
       part of the word before the left parenthesis has been defined using the
       define command will be recognized as a macro call with arguments;
       characters following the left parenthesis up to a matching right
       parenthesis will be treated as comma-separated arguments; commas inside
       nested parentheses do not terminate an argument.

       sdefine name X anything X
              This is like the define command, but name will not be recognized
              if called with arguments.

       include sfiles
              Include the contents of file. Lines of file beginning with .EQ
              or .EN will be 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.

   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.

       You can control which characters are treated as letters (and therefore
       set in italics) by using the chartype command described above.  A type
       of letter will cause a character to be set in italic type.  A type of
       digit will cause a character to be set in roman type.

FILES
       /usr/local/share/tmac/eqnrc
              Initialization file.

BUGS
       Inline equations will be set at the point size that is current at the
       beginning of the input line.

SEE ALSO
       groff(1), troff(1), groff_font(5), The TeXbook



Groff Version 1.15                                                9 April 2000
