eqn.man

早期freebsd实现

result.
.RS
.LP
For example, suppose you wanted a construct that `cancels' an expression
by drawing a diagonal line through it.
.IP
.nf
.ft B
.ne 6+\n(.Vu
\&.EQ
define cancel 'special Ca'
\&.EN
\&.de Ca
\&.ds 0s \eZ'\e\e*(0s'\ev'\e\en(0du'\eD'l \e\en(0wu -\e\en(0hu-\e\en(0du'\ev'\e\en(0hu'
\&..
.ft
.fi
.LP
Then you could cancel an expression
.I e
with
.BI cancel\ {\  e\  }
.LP
Here's a more complicated construct that draws a box round an expression:
.IP
.nf
.ft B
.ne 11+\n(.Vu
\&.EQ
define box 'special Bx'
\&.EN
\&.de Bx
\&.ds 0s \eZ'\eh'1n'\e\e*(0s'\e
\eZ'\ev'\e\en(0du+1n'\eD'l \e\en(0wu+2n 0'\eD'l 0 -\e\en(0hu-\e\en(0du-2n'\e
\eD'l -\e\en(0wu-2n 0'\eD'l 0 \e\en(0hu+\e\en(0du+2n''\eh'\e\en(0wu+2n'
\&.nr 0w +2n
\&.nr 0d +1n
\&.nr 0h +1n
\&..
.ft
.fi
.RE
.SS Customization
The appearance of equations is controlled by
a large number of parameters. These can be set using
the
.B set
command.
.TP
.BI set\  p\ n
This sets parameter
.I p
to value
.I n ;
.I n
is an integer.
For example,
.RS
.IP
.B
set x_height 45
.RE
.IP
says that
.B eqn
should assume an x height of 0.45 ems.
.RS
.LP
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.
.TP \w'\fBdefault_rule_thickness'u+2n
.B minimum_size
.B eqn
will not set anything at a smaller point-size than this.
The value is in points.
.TP
.B fat_offset
The
.B fat
primitive emboldens an equation
by overprinting two copies of the equation
horizontally offset by this amount.
.TP
.B 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.
.TP
.B accent_width
When
.B bar
or
.B under
is applied to a single character,
the line will be this long.
Normally,
.B bar
or
.B 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.
.TP
.B delimiter_factor
Extensible delimiters produced with the
.B left
and
.B 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.
.TP
.B delimiter_shortfall
Extensible delimiters produced with the
.B left
and
.B 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.
.TP
.B null_delimiter_space
This much horizontal space is inserted
on each side of a fraction.
.TP
.B script_space
The width of subscripts and superscripts is increased by this amount.
.TP
.B thin_space
This amount of space is automatically inserted after punctuation
characters.
.TP
.B medium_space
This amount of space is automatically inserted on either side
of binary operators.
.TP
.B thick_space
This amount of space is automatically inserted on either side of
relations.
.TP
.B x_height
The height of lowercase letters without ascenders such as x.
.TP
.B axis_height
The height above the baseline of the center of characters
such as \(pl and \(mi.
It is important that this value is correct for the font
you are using.
.TP
.B default_rule_thickness
This should set to the thickness of the
.B \e(ru
character, or the thickness of horizontal lines produced with the
.B \eD
escape sequence.
.TP
.B num1
The
.B over
command will shift up the numerator by at least this amount.
.TP
.B num2
The
.B smallover
command will shift up the numerator by at least this amount.
.TP
.B denom1
The
.B over
command will shift down the denominator by at least this amount.
.TP
.B denom2
The
.B smallover
command will shift down the denominator by at least this amount.
.TP
.B sup1
Normally superscripts will be shifted up by at least this amount.
.TP
.B sup2
Superscripts within superscripts or upper limits
or numerators of
.B smallover
fractions
will be shifted up by at least this amount.
This is usually less than sup1.
.TP
.B 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.
.TP
.B sub1
Subscripts will normally be shifted down by at least this amount.
.TP
.B sub2
When there is both a subscript and a superscript, the subscript
will be shifted down by at least this amount.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B big_op_spacing5
This much vertical space will be added above and below limits.
.TP
.B 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
.B num1
and
.BR denom1 .
.TP
.B 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
.BR axis_height .
.TP
.B column_sep
This much space will be added between columns in a matrix.
.TP
.B matrix_side_sep
This much space will be added at each side of a matrix.
.TP
.B draw_lines
If this is non-zero, lines will be drawn using the
.B \eD
escape sequence, rather than with the
.B \el
escape sequence and the
.B \e(ru
character.
.TP
.B 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
.BR \ex .)
The default value is 85.
.TP
.B 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
.BR \ex .)
The default value is 35.
.TP
.B nroff
If this is non-zero,
then
.B ndefine
will behave like
.B define
and
.B tdefine
will be ignored,
otherwise
.B tdefine
will behave like
.B define
and
.B ndefine
will be ignored.
The default value is 0
(This is typically changed to 1 by the
.B eqnrc
file for the
.B ascii
and
.B latin1
devices.)
.LP
A more precise description of the role of many of these
parameters can be found in Appendix H of
.IR The\ \*(txbook .
.RE
.SS Macros
Macros can take arguments.
In a macro body,
.BI $ n
where
.I n
is between 1 and 9,
will be replaced by the
.IR n-th
argument if the macro is called with arguments;
if there are fewer than
.I 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
.B 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.
.TP
.BI sdefine\  name\ X\ anything\ X
This is like the
.B define
command, but
.I name
will not be recognized if called with arguments.
.TP
.BI include\ \(ts file \(ts
Include the contents of
.IR file .
Lines of
.I file
beginning with
.B .EQ
or
.B .EN
will be ignored.
.TP
.BI ifdef\  name\ X\ anything\ X
If
.I name
has been defined by
.B define
(or has been automatically defined because
.I name
is the output device)
process
.IR anything ;
otherwise ignore
.IR anything .
.I X
can be any character not appearing in
.IR anything .
.SS Fonts
.B 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
.B gfont
command
changes the font that is used as the italic font.
By default this is
.BR I .
The font that is used as the roman font can be changed
using the new
.B grfont
command.
.TP
.BI grfont\  f
Set the roman font to
.IR f .
.LP
The
.B italic
primitive uses the current italic font set by
.BR gfont ;
the
.B roman
primitive uses the current roman font set by
.BR grfont .
There is also a new
.B gbfont
command, which changes the font used by the
.B bold
primitive.
If you only use the
.BR roman ,
.B italic
and
.B bold
primitives to changes fonts within an equation,
you can change all the fonts used by your equations
just by using
.BR gfont ,
.B grfont
and
.B gbfont
commands.
.LP
You can control which characters are treated as letters
(and therefore set in italics) by using the
.B chartype
command described above.
A type of
.B letter
will cause a character to be set in italic type.
A type of
.B digit
will cause a character to be set in roman type.
.SH FILES
.Tp \w'\fB@MACRODIR@/eqnrc'u+2n
.B @MACRODIR@/eqnrc
Initialization file.
.SH BUGS
Inline equations will be set at the point size that is current at the
beginning of the input line.
.SH "SEE ALSO"
.BR groff (@MAN1EXT@),
.BR @g@troff (@MAN1EXT@),
.BR groff_font (@MAN5EXT@),
.I The\ \*(txbook