EQN(1)

NAME
eqn, neqn, checkeq - typeset mathematics

SYNOPSIS
eqn [ -dxy ] [ -pn ] [ -sn ] [ -fn ] [ file ] ...
checkeq [ file ] ...

DESCRIPTION
Eqn is a troff(1) preprocessor for typesetting mathematics on a Graphic Systems phototypesetter, neqn on terminals. Usage is almost always

    eqn file ... | troff
    neqn file ... | nroff

If no files are specified, these programs read from the standard input. A line beginning with `.EQ' marks the start of an equation; the end of an equation is marked by a line beginning with `.EN'. Neither of these lines is altered, so they may be defined in macro packages to get centering, numbering, etc. It is also possible to set two characters as `delimiters'; subsequent text between delimiters is also treated as eqn input. Delimiters may be set to characters x and y with the command-line argument -dxy or (more commonly) with `delim xy' between .EQ and .EN. The left and right delimiters may be identical. Delimiters are turned off by `delim off'. All text that is neither between delimiters nor between .EQ and .EN is passed through untouched.

The program checkeq reports missing or unbalanced delimiters and .EQ/.EN pairs.

Tokens within eqn are separated by spaces, tabs, newlines, braces, double quotes, tildes or circumflexes. Braces {} are used for grouping; generally speaking, anywhere a single character like x could appear, a complicated construction enclosed in braces may be used instead. Tilde ~ represents a full space in the output, circumflex ^ half as much.

Subscripts and superscripts are produced with the keywords sub and sup. Thus x sub i makes $x sub i$, a sub i sup 2 produces $a sub i sup 2$, and e sup {x sup 2 + y sup 2} gives $e sup {x sup 2 + y sup 2}$.

Fractions are made with over: a over b yields $a over b$.

sqrt makes square roots: 1 over sqrt {ax sup 2 +bx+c} results in $1 over sqrt {ax sup 2 +bx+c}$ .

The keywords from and to introduce lower and upper limits on arbitrary things: $lim from {n-> inf} sum from 0 to n x sub i$ is made with lim from {n-> inf } sum from 0 to n x sub i.

Left and right brackets, braces, etc., of the right height are made with left and right: left [ x sup 2 + y sup 2 over alpha right ] ~=~1 produces $left [ x sup 2 + y sup 2 over alpha right ] ~=~1$. The right clause is optional. Legal characters after left and right are braces, brackets, bars, c and f for ceiling and floor, and "" for nothing at all (useful for a right-side-only bracket).

Vertical piles of things are made with pile, lpile, cpile, and rpile: pile {a above b above c} produces $pile {a above b above c}$. There can be an arbitrary number of elements in a pile. lpile left-justifies, pile and cpile center, with different vertical spacing, and rpile right justifies.

Matrices are made with matrix: matrix { lcol { x sub i above y sub 2 } ccol { 1 above 2 } } produces $matrix { lcol { x sub i above y sub 2 } ccol { 1 above 2 } }$. In addition, there is rcol for a right-justified column.

Diacritical marks are made with dot, dotdot, hat, tilde, bar, vec, dyad, and under: x dot = f(t) bar is $x dot = f(t) bar$, y dotdot bar ~=~ n under is $y dotdot bar ~=~ n under$, and x vec ~=~ y dyad is $x vec ~=~ y dyad$.

Sizes and font can be changed with size n or size ±n, roman, italic, bold, and font n. Size and fonts can be changed globally in a document by gsize n and gfont n, or by the command-line arguments -sn and -fn.

Normally subscripts and superscripts are reduced by 3 point sizes from the previous size; this may be changed by the command-line argument -pn.

Successive display arguments can be lined up. Place mark before the desired lineup point in the first equation; place lineup at the place that is to line up vertically in subsequent equations.

Shorthands may be defined or existing keywords redefined with define: define thing % replacement % defines a new token called thing which will be replaced by replacement whenever it appears thereafter. The % may be any character that does not occur in replacement.

Keywords like sum int inf and shorthands like >= -> and != are recognized. Greek letters are spelled out in the desired case, as in alpha or GAMMA. Mathematical words like sin, cos, log are made Roman automatically. Troff(1) four-character escapes like \(bs () can be used anywhere. Strings enclosed in double quotes "..." are passed through untouched; this permits keywords to be entered as text, and can be used to communicate with troff when all else fails.

A compatible version of eqn can be used on devices which have half-line forward and reverse capabilities. To print on such devices use

    neqn file ... | nroff

The language for equations recognized by neqn is identical to that of eqn, although of course the output is more restricted. To print on devices which do not have half-line capabilities it may be necessary to pass the output from nroff(1) through col(1), which will strip the half-line forward and reverse line feeds and produce more sensible output. For example,

    neqn file ... | nroff | col

Note that this restricts the output even more and only an approximation to the desired result may be possible for certain equations.

SEE ALSO

troff(1), tbl(1), nroff(1), col(1), ms(7), eqnchar(7)
B. W. Kernighan and L. L. Cherry, Typesetting Mathematics—User's Guide
J. F. Ossanna, NROFF/TROFF User's Manual

BUGS

To embolden digits, parens, etc., it is necessary to quote them, as in `bold "12.3"'.