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Page 204

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


.EQ

define cancel `special Ca'

.EN

.de Ca

.ds 0s \Z'\\*(0s'\v'\\n(0du'\D'l \\n(0wu -\\n(0hu-\\n(0du'\v'\\n(0hu'

..

Then you could cancel an expression U with cancel e.

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


.EQ

define box `special Bx'

.EN

.de Bx

.ds 0s \Z'\h'1n'\\*(0s'\

\Z'\v'\\n(0du+1n'\D'l \\n(0wu+2n 0'\D'l 0 -\\n(0hu-\\n(0du-2n'\

\D'l -\\n(0wu-2n 0'\D'l 0 \\n(0hu+\\n(0du+2n"\h'\\n(0wu+2n'

.nr 0w +2n

.nr 0d +1n

.nr 0h +1n

..

CUSTOMIZATION

The appearance of equations is controlled by a large number of parameters. These can be set using the set command.

setpn This sets parameter p to value n; n is an integer. For example set x_height 45 says that eqn should assume an x height of 0.45 ems.

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.

minimum_size eqn will not set anything at a smaller point size than this. The value is in points.
fat_offset The fat primitive emboldens an equation by overprinting two copies of the equation horizontally offset by this amount.
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.
accent_width When bar or under is applied to a single character, the line will be this long. Normally, bar or 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.
delimiter_factor Extensible delimiters produced with the left and right primitives will have a combined height and depth of at least this many thousandths of twice the maximum amount by which the subequation that the delimiters enclose extends away from the axis.
delimiter_shortfall Extensible delimiters produced with the left and right primitives will have a combined height and depth not less than the difference of twice the maximum amount by which the subequation that the delimiters enclose extends away from the axis and this amount.
null_delimiter_space This much horizontal space is inserted on each side of a fraction.
script_space The width of subscripts and superscripts is increased by this amount.
thin_space This amount of space is automatically inserted after punctuation characters.
medium_space This amount of space is automatically inserted on either side of binary operators.
thick_space This amount of space is automatically inserted on either side of relations.

Page 205

 x_height The height of lowercase letters without ascenders such as x. axis_height The height above the baseline of the center of characters such as + and -. It is important that this value be correct for the font you are using. default_rule_thickness This should set to the thickness of the \(ru character, or the thickness of horizontal lines produced with the \D escape sequence. num1 The over command will shift up the numerator by at least this amount. num2 The smallover command will shift up the numerator by at least this amount. denom1 The over command will shift down the denominator by at least this amount. denom2 The smallover command will shift down the denominator by at least this amount. sup1 Normally superscripts will be shifted up by at least this amount. sup2 Superscripts within superscripts or upper limits or numerators of smallover fractions will be shifted up by at least this amount. This is usually less than sup1. 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. sub1 Subscripts will normally be shifted down by at least this amount. sub2 When there is both a subscript and a superscript, the subscript will be shifted down by at least this amount. sup_drop The baseline of a superscript will be no more than this amount below the top of the object on which the superscript is set. 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. 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. 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. 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. 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. big_op_spacing5 This much vertical space will be added above and below limits. 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 num1 and denom1. 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 axis_height. column_sep This much space will be added between columns in a matrix. matrix_side_sep This much space will be added at each side of a matrix. draw_lines If this is nonzero, lines will be drawn using the \D escape sequence, rather than with the \l escape sequence and the \(ru character. 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 \x.) The default value is 85. 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 \x.) The default value is 35. nroff If this is nonzero, then ndefine will behave like define and tdefine will be ignored; otherwise, tdefine will behave like define and ndefine will be ignored. The default value is 0. (This is typically changed to 1 by the eqnrc file for the ascii and latin1 devices.)

A more precise description of the role of many of these parameters can be found in Appendix H of The TeXbook.

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