4.5 Error Handling in LL (1)Parsing
Much work has been done in error handling for parser generators. Some
perform a recovery process so that parsing may continue; a few try to
repair the error. Topdown parsers detect the erroneous token when it is
shifted onto the stack. An error report might be
Unexpected erroneous token
with the parser driver attempting a recovery based upon the choices that
would have been valid instead of the errorneous token. The attempted
recovery, adding or deleting tokens, may be made to either the stack or the
input. Error handling similar to that used for recursive descent parsing is
described in Lemone (1992). The method was developed by Niklaus Wirth in
1976. It requires that a set of firsts and followers be maintained or
computed for each production.
