31.9 Additional recoverable failures in marpa_r_alternative()

Among the hard failures that marpa_r_alternative() returns are the error codes MARPA_ERR_DUPLICATE_TOKEN, MARPA_ERR_NO_TOKEN_EXPECTED_HERE and MARPA_ERR_INACCESSIBLE_TOKEN. These are currently irrecoverable. They may in fact be fully recoverable, but are not documented as such because this has not been tested.

At this writing, we know of no applications that attempt to recover from these errors. It is possible that these error codes may also be useable for the techniques similar to the Ruby Slippers, as of this writing, we know of no proposals to use them in this way.