eqn.man

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.\" The BSD man macros can't handle " in arguments to font change macros,
.\" so use \(ts instead of ".
.tr \(ts"
.TH @G@EQN @MAN1EXT@ "@MDATE@" "Groff Version @VERSION@"
.SH NAME
@g@eqn \- format equations for troff
.SH SYNOPSIS
.B @g@eqn
[
.B \-rvCNR
]
[
.BI \-d cc
]
[
.BI \-T name
]
[
.BI \-M dir
]
[
.BI \-f F
]
[
.BI \-s n
]
[
.BI \-p n
]
[
.BI \-m n
]
[
.IR files \|.\|.\|.
]
.SH DESCRIPTION
This manual page describes the GNU version of
.BR eqn ,
which is part of the groff document formatting system.
.B eqn
compiles descriptions of equations embedded within
.B troff
input files into commands that are understood by
.BR troff .
Normally, it should be invoked using the
.B \-e
option of
.BR 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
.B \-
will cause the standard input to be read.
.LP
.B eqn
searches for the file
.B eqnrc
using the path
.BR @MACROPATH@ .
If it exists, eqn will process it before the other input files.
The
.B \-R
option prevents this.
.LP
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).
.SH OPTIONS
.TP
.B \-C
Recognize
.B .EQ
and
.B .EN
even when followed by a character other than space or newline.
.TP
.B \-N
Don't allow newlines within delimiters.
This option allows
.B eqn
to recover better from missing closing delimiters.
.TP
.B \-v
Print the version number.
.TP
.B \-r
Only one size reduction.
.TP
.BI \-m n
The minimum point-size is
.IR n .
eqn will not reduce the size of subscripts or superscripts to
a smaller size than
.IR n .
.TP
.BI \-T name
The output is for device
.IR name .
The only effect of this is to define a macro
.I name
with a value of
.BR 1 .
Typically
.B eqnrc
will use this to provide definitions appropriate for the output device.
The default output device is
.BR @DEVICE@ .
.TP
.BI \-M dir
Search
.I dir
for
.B eqnrc
before the default directories.
.TP
.B \-R
Don't load
.BR eqnrc .
.TP
.BI \-f F
This is equivalent to a
.BI gfont\  F
command.
.TP
.BI \-s n
This is equivalent to a
.BI gsize\  n
command.
This option is deprecated.
eqn will normally set equations at whatever the current point size
is when the equation is encountered.
.TP
.BI \-p n
This says that subscripts and superscripts should be
.I 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.
.SH USAGE
Only the differences between GNU eqn and Unix eqn are described here.
.LP
Most of the new features of GNU eqn
are based on \*(tx.
There are some references to the differences between \*(tx and GNU eqn below;
these may safely be ignored if you do not know \*(tx.
.SS Automatic spacing
.LP
.B eqn
gives each component of an equation a type, and adjusts the spacing
between components using that type.
Possible types are:
.TP \w'punctuation'u+2n
ordinary
an ordinary character such as 1 or
.IR x ;
.TP
operator
a large operator such as
.ds Su \s+5\(*S\s0
.if \n(.g .if !c\(*S .ds Su the summation operator
\*(Su;
.TP
binary
a binary operator such as +;
.TP
relation
a relation such as =;
.TP
opening
a opening bracket such as (;
.TP
closing
a closing bracket such as );
.TP
punctuation
a punctutation character such as ,;
.TP
inner
a subformula contained within brackets;
.TP
suppress
spacing that suppresses automatic spacing adjustment.
.LP
Components of an equation get a type in one of two ways.
.TP
.BI type\  t\ e
This yields an equation component that contains
.I e
but that has type
.IR t ,
where
.I t
is one of the types mentioned above.
For example,
.B times
is defined as
.RS
.IP
.B
type "binary" \e(mu
.RE
.IP
The name of the type doesn't have to be quoted, but quoting protects
from macro expansion.
.TP
.BI 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
.I text
from now on have type
.IR t .
For example,
.RS
.IP
.B
chartype "punctuation" .,;:
.RE
.IP
would make the characters
.B .,;:
have type punctuation
whenever they subsequently appeared in an equation.
The type
.I t
can also be
.B letter
or
.BR digit ;
in these cases
.B chartype
changes the font type of the characters.
See the Fonts subsection.
.SS New primitives
.TP
.IB e1\  smallover\  e2
This is similar to
.BR over ;
.B smallover
reduces the size of
.I e1
and
.IR e2 ;
it also puts less vertical space between
.I e1
or
.I e2
and the fraction bar.
The
.B over
primitive corresponds to the \*(tx
.B \eover
primitive in display styles;
.B smallover
corresponds to
.B \eover
in non-display styles.
.TP
.BI vcenter\  e
This vertically centers
.I 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,
.B sum
is defined as
.RS
.IP
.B
{ type "operator" vcenter size +5 \e(*S }
.RE
.TP
.IB e1\  accent\  e2
This sets
.I e2
as an accent over
.IR e1 .
.I e2
is assumed to be at the correct height for a lowercase letter;
.I e2
will be moved down according if
.I e1
is taller or shorter than a lowercase letter.
For example,
.B hat
is defined as
.RS
.IP
.B
accent { "^" }
.RE
.IP
.BR dotdot ,
.BR dot ,
.BR tilde ,
.B vec
and
.B dyad
are also defined using the
.B accent
primitive.
.TP
.IB e1\  uaccent\  e2
This sets
.I e2
as an accent under
.IR e1 .
.I e2
is assumed to be at the correct height for a character without a descender;
.I e2
will be moved down if
.I e1
has a descender.
.B utilde
is pre-defined using
.B uaccent
as a tilde accent below the baseline.
.TP
.BI split\ \(ts text \(ts
This has the same effect as simply
.RS
.IP
.I text
.RE
.IP
but
.I text
is not subject to macro expansion because it is quoted;
.I text
will be split up and the spacing between individual characters
will be adjusted.
.TP
.BI nosplit\  text
This has the same effect as
.RS
.IP
.BI \(ts text \(ts
.RE
.IP
but because
.I text
is not quoted it will be subject to macro expansion;
.I text
will not be split up
and the spacing between individual characters will not be adjusted.
.TP
.IB e\  opprime
This is a variant of
.B prime
that acts as an operator on
.IR e .
It produces a different result from
.B prime
in a case such as
.BR A\ opprime\ sub\ 1 :
with
.B opprime
the
.B 1
will be tucked under the prime as a subscript to the
.B A
(as is conventional in mathematical typesetting),
whereas with
.B prime
the
.B 1
will be a subscript to the prime character.
The precedence of
.B opprime
is the same as that of
.B bar
and
.BR under ,
which is higher than that of everything except
.B accent
and
.BR uaccent .
In unquoted text a
.B '
that is not the first character will be treated like
.BR opprime .
.TP
.BI special\  text\ e
This constructs a new object from
.I e
using a
.BR @g@troff  (@MAN1EXT@)
macro named
.IR text .
When the macro is called,
the string
.B 0s
will contain the output for
.IR e ,
and the number registers
.BR 0w ,
.BR 0h ,
.BR 0d ,
.BR 0skern
and
.BR 0skew
will contain the width, height, depth, subscript kern, and skew of
.IR e .
(The
.I "subscript kern"
of an object says how much a subscript on that object should be tucked in;
the
.I 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
.B 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