The package provides macros for typesetting math formulas in mixed horizontal and vertical mode, automatically as best fit. It provides an environment mathpar that behaves much as a loose centered paragraph where words are math formulas, and spaces between them are larger and adjustable. It also provides a macro \inferrule for typesetting fractions where both the numerator and denominator may be sequences of formulas that will be also typeset in a similar way. It can typically be used for typeseting sets of type inference rules or typing derivations.