## SYNOPSIS

           eqn [ -rvCNR ] [ -dcc ] [ -Tname ] [ -Mdir ] [ -fF ]
               [ -sn ] [ -pn ] [ -mn ] [ 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 com
           piles  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 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 stan
           dard  macro directory /usr/share/groff/1.17.2/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 char
                  acter 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  defini
                  tions  appropriate  for  the  output  device.   The
                  default output device is ps.

                  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 ¯</I<B>>;

           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 charac
                  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  frac
                  tions.  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 "text"
                  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

                         "text"

                  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

           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, sub
                  script 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  can
                  cel { 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  num
           ber of parameters. These can be set using the set command.

                  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 charac
                                          ter,  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 pro
                                          duced  with  the  left  and
                                          right  primitives will have
                                          a combined height and depth
                                          of at least this many thou
                                          sandths of twice the  maxi
                                          mum  amount  by  which  the
                                          sub-equation    that    the
                                          delimiters  enclose extends
                                          away from the axis.

                  delimiter_shortfall     Extensible delimiters  pro
                                          duced  with  the  left  and
                                          right primitives will  have
                                          a combined height and depth
                                          not less than  the  differ
                                          ence  of  twice the maximum
                                          amount by  which  the  sub-
                                          equation  that  the  delim
                                          iters enclose extends  away
                                          ters.

                  medium_space            This  amount  of  space  is
                                          automatically  inserted  on
                                          either side of binary oper
                                          ators.

                  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  base
                                          line of the center of char
                                          acters 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 char
                                          acter,  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  super
                                          scripts  or upper limits or
                                          numerators   of   smallover
                                          this amount.

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

                  sup_drop                The  baseline  of  a super
                                          script 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  sub
                                          script 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

                  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 char
                                          acter.

                  body_height             The  amount  by  which  the
                                          height  of   the   equation
                                          exceeds  this will be added
                                          as extra space  before  the
                                          line  containing  the equa
                                          tion   (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 equa
                                          tion   (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,  latin1,  utf8,
                                          and cp1047 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
                  If  name  has  been  defined by define (or has been
                  automatically defined because name  is  the  output
                  device)  process  anything;  otherwise  ignore any
                  thing.  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  every
           thing  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 com
           mands.

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

## FILES

           /usr/share/groff/1.17.2/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 1.17.2       27 June 2001                    EQN(1)