Frac

A fraction with numerator and denominator styles, baseline shifts, and clearance around its rule. Generalized fractions can omit the rule or add delimiters.

Property	Default	Meaning
children	Required	Exactly two operands: numerator, then denominator.
has_bar	true	Draw the fraction rule; false uses no-bar clearance.
thickness	Style metric	Rule thickness as a Gum length, such as px(2) or em(0.04).
continued	false	Reserve a continued-fraction numerator strut and omit right-side padding/delimiter.
padding	TeX null-delimiter space	Horizontal padding on sides without a delimiter.
left_delim / right_delim	Absent	Delimiters selected at the style's fraction delimiter height.
style / size_index	Inherited	Fraction style and optional TeX size index.
klass / left / right	"mord"	Classes exposed by the fraction.

TeX supports \frac, \dfrac, \tfrac, \cfrac, binomials, infix \over/\atop/\choose, and \genfrac. Generalized fractions preserve bar thickness, delimiters, and style. Absolute TeX dimensions keep their size in scripts; public Gum em() thickness uses the active math em.

The denominator is cramped. Without a bar, clearance is measured between the two operands rather than reserving space around an invisible rule. See ordinary formulas.