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eqn(1)

NAME

       eqn - format equations for troff

SYNOPSIS

       eqn [ -rvCNR ] [ -dxy ] [ -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 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 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/share/tmac, /usr/share/tmac, and finally  in
       the  standard  macro directory /usr/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  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 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.

       -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  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
	      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.

       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 "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 charac-
	      ters 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 mathemati-
	      cal 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	every-
	      thing  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
	      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 parame-
       ters. These can be set using the set command.

       set p n
	      This sets parameter p to value n ; n is an integer.   For  exam-
	      ple,

		     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  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  equa-
				      tion 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
				      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 maxi-
				      mum  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 opera-
				      tors.

	      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  cor-
				      rect for the font you are using.

	      default_rule_thickness  This  should set to the thickness of the
				      \(ru character, or the thickness of hor-
				      izontal	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
				      this  amount.  This is usually less than
				      sup1.

	      sup3		      Superscripts  within   denominators   or
				      square roots or subscripts or lower lim-
				      its 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
				      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 typi-
				      cally 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  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, 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; char-
       acters  following the left parenthesis up to a matching right parenthe-
       sis 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 "file"
	      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.

       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/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 1.19		11 October 2002 			EQN(1)

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