After an updated of AUCTeX (to 11.87) the solution that worked wonderful from this answer stopped working. In particular, I got the following error:
reftex-reference: Wrong number of arguments: (lambda (label def-fmt) (format "\\cref{%s}" label)), 3
As a side remark, for this solution to be usable I had to add (setq reftex-ref-macro-prompt nil), otherwise an annoying intermediate menu poped-up. I guess it has to do with the update as well, but it is not related to the problem I'm considering in this question.
In turn, I found this answer (of @giordano) which solved the issue (once I disabled the previous hack). However, there is one problem left - when I try to refer to an equation, namely, M-x reftex-reference RET e up/down RET, the system inserts \eqref{label} and not \cref{label}. Is there a way to fix this? Any idea?
reftex-reference?) should be redefined. I suggest you to report this to AUCTeX mailing list. – giordano Oct 06 '13 at 10:10