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To achieve more of the benefits of both models, we extend the pattern syntax of awk to support matching of abstract syntax trees, as demonstrated in a tool called tawk. Its pattern syntax is language-independent, based on abstract tree patterns. As in awk, patterns can have associated actions, which in tawk are written in C for generality, familiarity, and performance. The use of C is simplified by high-level libraries and dynamic linking. To allow processing of program files containing non-syntactic constructs, mechanisms have been designed that allow transparent matching in a syntactic fashion. So far, tawk has been retargeted to the MUMPS and C programming languages.
We survey and apply prototypical approaches to concretely demonstrate the tradeoffs. Our results indicate that tawk can be used to quickly and easily perform a variety of common software engineering tasks, and the extensions to accommodate non-syntactic features significantly extend the generality of syntactic matchers.