  LaTeX is a widely-used document preparation system. Its powerful ability in
mathematical equation editing is perhaps the main reason for its popularity in
academia. Sometimes, however, even an expert user may spend much time fixing an
erroneous equation. In this paper, we present EqFix, a synthesis-based
repairing system for LaTeX equations. It employs a set of fixing rules and can
suggest possible repairs for common errors in LaTeX equations. A
domain-specific language is proposed for formally expressing the fixing rules.
The fixing rules can be automatically synthesized from a set of input-output
examples. An extension of relaxers is also introduced to enhance the
practicality of EqFix. We evaluate EqFix on real-world examples and find that
it can synthesize rules with high generalization ability. Compared with a
state-of-the-art string transformation synthesizer, EqFix solved 37% more cases
and spent less than half of their synthesis time.
