Pushback on parsers. It's very difficult to provide useful diagnostic error messages with yacc/bison. So most languages end up with a hand-written recursive de

Pushback on parsers. It's very difficult to provide useful diagnostic error messages with yacc/bison. So most languages end up with a hand-written recursive descent parser. The only exception I personally know of is jq (uses bison). So it's difficult to produce helpful syntax error messages in the implementation of jq.