Automatic spacing

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 example, times is defined as

The name of the type doesn't have to be quoted, but quoting protects from macro expansion.

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 text from now on have type t. For example,

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.

New primitives

big e

Enlarges the expression it modifies; intended to have semantics like CSS `large'. In troff output, the point size is increased by 5; in MathML output, the expression uses

e1 smallover e2

This is similar to over; smallover reduces the size of e1 and e2; it also puts less vertical space between e1 or e2 and the fraction bar. The over primitive corresponds to the TeX \over primitive in display styles; smallover corresponds to \over in non-display styles.

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

(Note that vcenter is silently ignored when generating MathML.)

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 is moved down according to whether e1 is taller or shorter than a lowercase letter. For example, hat is defined as

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 is 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

but text is not subject to macro expansion because it is quoted; text is split up and the spacing between individual characters is adjusted.

nosplit text

This has the same effect as

but because text is not quoted it is subject to macro expansion; text is not split up and the spacing between individual characters is not 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 is tucked under the prime as a subscript to the A (as is conventional in mathematical typesetting), whereas with prime the 1 is 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 everything except accent and uaccent. In unquoted text a ' that is not the first character is 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 contains the output for e, and the number registers 0w, 0h, 0d, 0skern, and 0skew contain the width, height, depth, subscript kern, and skew of e. (The subscript kern of an object says how much a subscript on that object should be tucked in; the 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 0s so that it outputs 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 result.

For example, suppose you wanted a construct that `cancels' an expression by drawing a diagonal line through it.

Then you could cancel an expression e with cancel { e }

Here's a more complicated construct that draws a box round an expression:

space n

A positive value of the integer n (in hundredths of an em) sets the vertical spacing before the equation, a negative value sets the spacing after the equation, replacing the default values. This primitive provides an interface to groff's \x escape (but with opposite sign).

This keyword has no effect if the equation is part of a pic picture.

Extended primitives

col n { ... }

ccol n { ... } lcol n { ... } rcol n { ... } pile n { ... } cpile n { ... } lpile n { ... } rpile n { ... } The integer value n (in hundredths of an em) increases the vertical spacing between rows, using groff's \x escape (the value has no effect in MathML mode). Negative values are possible but have no effect. If there is more than a single value given in a matrix, the biggest one is used.

Customization

set p n

This sets parameter p to value n; n is an integer. For example,

says that eqn should assume an x height of 0.45 ems.

Macros

sdefine name X anything X

This is like the define command, but name is not recognized if called with arguments.

include "file"

copy "file" Include the contents of file (include and copy are synonyms). Lines of file beginning with .EQ or .EN are 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.

undef name

Remove definition of name, making it undefined.

Fonts

grfont f

Set the roman font to f.