I've had the chance to build parsers for work. Once for a templating engine for SQL (taking values from the environment and using them queries). This was reall

I've had the chance to build parsers for work. Once for a templating engine for SQL (taking values from the environment and using them queries). This was really nice for productivity and an intern could churn out dozens of reports a day. That was written with javacc. Another time by using a parser (written with Antlr) to extract bits of PLSQL packages (procedures, functions) and move them from one environment to another without having to send the whole package. Although this type of job is rare, it can be really useful when it shows up.