  In this paper we study function-correcting codes, a new class of codes
designed to protect the function evaluation of a message against errors. We
show that FCCs are equivalent to irregular-distance codes, i.e., codes that
obey some given distance requirement between each pair of codewords. Using
these connections, we study irregular-distance codes and derive general upper
and lower bounds on their optimal redundancy. Since these bounds heavily depend
on the specific function, we provide simplified, suboptimal bounds that are
easier to evaluate. We further employ our general results to specific functions
of interest and compare our results to standard error-correcting codes, which
protect the whole message.
