Reparse

Due to the possibility that a reparse may be necessary, it is crucial that the parsing of a command should avoid any irrevocable alteration in the state of the data structures until the command is confirmed.

In the case of less vicious examples, the alternate parse may be readily available as a parallel hypothesis, but in the vicious example cited above, a reparse is started with a different set of expectations for the syntactic role of what is being parsed.