neqn(1)

NAME

neqn — format mathematical text for nroff

SYNOPSIS

neqn [-d xy] [-s n] [-f n] [-p n] [file ...]

Note

The output of neqn is very device-dependent. See the "WARNINGS" section.

DESCRIPTION

neqn is a preprocessor for nroff (see nroff(1)) for typesetting mathematical text on typewriter-like terminals. Its invocation is almost always of the following two forms or equivalent:

neqn files | nroff | col
tbl files | neqn | nroff | col

If no files are specified (or if - is specified instead of file), neqn reads from 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, which means that they can be defined in macro packages to get centering, numbering, etc.

It is also possible to designate two characters as delimiters; subsequent text between delimiters is then treated as neqn input. Delimiters can be set to characters x and y with the command-line argument -dxy or (more commonly) with the sequence

.EQ delim xy .EN

The left and right delimiters can be the same character; the dollar sign ($) is often used as such a delimiter. Delimiters are turned off by delim off (see the "WARNINGS" section). All text that is neither between delimiters nor between .EQ and .EN is passed through untouched. delim $$

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

Subscripts and Superscripts

Subscripts and superscripts are produced using sub and sup as follows:

Source Text: Result
x sub j: $x sub j$
a sub k sup 2: $a sub k sup 2$
e sup {x sup 2 + y sup 2}: $e sup {x sup 2 + y sup 2}$

Fractions

Fractions are produced by using over:

Source Text: Result
a over b: $a over b$

Square Roots

sqrt produces square roots:

Source Text: Result
1 over sqrt {ax sup 2+bx+c}: $1 over sqrt {ax sup 2 +bx+c}$

Upper and Lower Limits

The keywords from and to specify lower and upper limits:

Source Text: Result
lim from {n -> inf } sum from 0 to n x sub i: $lim from {n -> inf} ~ sum from 0 to n ~ x sub i$

Brackets and Braces

Left and right brackets, braces, and such, of proper height are made with left and right:

Source Text: Result
left [ {x sup 2 + y sup 2}
over alpha right ] ~=~ 1: $left [ {x sup 2 + y sup 2} over alpha right ] ~=~ 1$

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). A left char need not have a matching right char.

Vertical Piles

Vertical piles of elements are made with pile, lpile, cpile, and rpile:

Source Text: Result
pile {a above bb above ccc}: $pile {a above bb above ccc}$

Piles can have arbitrary numbers of elements; lpile left justifies, pile and cpile center (but with different vertical spacing), and rpile right justifies.

Matrices and Determinants

Matrices are made with matrix:

Source Text: Result
left | { matrix {
lcol { x sub i above y sub 2 }
ccol { 1 above 234 } } } right |: $left | { matrix { lcol { x sub i above y sub 2 } ccol { 1 above 234 } } } right |$

In addition, there is rcol for a right-justified column.

Diacritical Marks

Diacritical marks are made with dot, dotdot, hat, tilde, bar, vec, dyad, and under:

Source Text: Result
x dot = f(t) bar: $x dot = f(t) bar$
y dotdot bar ~=~ n under: $y dotdot bar ~=~ n under$
x vec ~=~ y dyad: $x vec ~=~ y dyad$

delim off

Point Sizes and Fonts

Point sizes and fonts can be changed with size n or size +|-n, roman, italic, bold, and font n. Point sizes 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 points from the previous size; this can be changed by the command-line argument -pn.

Vertical Alignment

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.

Shorthand Forms

Shorthand forms can be defined or existing keywords redefined with define:

define thing % replacement %

defines a new token called thing that is replaced by replacement whenever it appears thereafter. The % can be any character that does not occur in replacement.

Other Keywords

Keywords such as sum ( sum ), int ( int ), inf ( inf ), and shorthands such as >= (>=), != ( != ), and -> (->) are recognized. Greek letters are spelled out in uppercase or lowercase as desired, as in alpha ( alpha ) or GAMMA ( GAMMA ). Mathematical words such as sin, cos, and log are made Roman automatically. nroff four-character escapes such as \(dd (**) and \(bu (•) can be used anywhere.

Verbatim Text

Strings enclosed in double quotes (" string " ) are passed through untouched; this permits keywords to be entered as text, and can be used to communicate with nroff when other methods fail. Details are given in the manuals cited below.

EXTERNAL INFLUENCES

Environment Variables

LC_CTYPE determines the interpretation of text as single- or multibyte characters.

LANG determines the language in which messages are displayed.

If LC_CTYPE is not specified in the environment or is set to the empty string, the value of LANG is used as a default for each unspecified or empty variable. If LANG is not specified or is set to the empty string, a default of "C" (see lang(5)) is used instead of LANG. If any internationalization variable contains an invalid setting, neqn behaves as if all internationalization variables are set to "C". See environ(5).

International Code Set Support

Single- and multibyte character code sets are supported.

WARNINGS

To embolden digits, parentheses, etc., it is necessary to quote them, as in bold "12.3" Also see the "WARNINGS" section in nroff(1).

Good practice dictates that if a delimiter is specified in a file, the delim off directive should be included at the end of the file to prevent undesirable behavior when processing multiple files where a subsequent file may contain the delimiter character as part of regular text.

To properly display equations on terminal screens and other devices that do not support reverse line feeds, nroff output should be piped through col (see col(1)).

The display on devices that do not support partial linefeeds is often difficult to understand; Greek characters and other symbols are often not well supported and can mismatched printing of bold words on the same line (see a printed version of the "Other Keywords" subsection above). Consider using "computer-program" coding instead.