A simple table look-up parser (TLUP) has been developed for parsing and consequently diagnosing syntactic errors in semi-free formatted learners' input sentences of an intelligent language tutoring system (ILTS). The TLUP finds a parse tree for a correct version of an input sentence, diagnoses syntactic errors of the learner by tracing and regarding the deviations of the input from the identified correct sentences as errors of the learner. The TLUP can now display the parse tree as well as diagnosed errors at leaves' level. This simple super-rule based TLUP turns out to be a powerful pedagogic tool coaching L2 (second language) learners on the grammar structures in L2, saving the computing time and running space requirements, improving the parsing accuracy and allowing the real time online running environments to be applicable. The TLUP is effective as long as the input does not deviate too much from anticipated embedded patterns of model answers with committed errors remaining within the framework of anticipation for the level of the ITLS designed. We establish the validity of a TLUP by an (n, c) lot acceptance?sampling plan.