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 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  using  the  path
       .:/usr/lib/groff/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.

       -Mdir  Search  dir  for  eqnrc before the default directo-
              ries.

       -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 equa-
              tions 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 the summation opera-
                    tor;

       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-
              ter is looked up; this changes  the  type  that  is
              stored for each character; it says that the charac-
              ters in text from now on have type t.  For example,

                     chartype "punctuation" .,;:

              would  make  the characters .,;: have type punctua-
              tion 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 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
              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  typeset-
              ting), 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,  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
              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 num-
       ber 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 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
                                      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  charac-
                                      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
                                      fractions will  be  shifted
                                      up by at least this amount.
                                      This is usually  less  than
                                      sup1.

              sup3                    Superscripts within denomi-
                                      nators 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  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
                                      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 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   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-sep-
       arated  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 "file"
              Include the contents of file.  Lines of file begin-
              ning 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  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/lib/groff/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 1.11         26 June 1995                         1