Making YACC output an AST (token tree)

Question

Is it possible to make YACC (or I'm my case MPPG) output an Abstract Syntax Tree (AST).

All the stuff I'm reading suggests its simple to make YACC do this, but I'm struggling to see how you know when to move up a node in the tree as your building it.

Answer 1

Have you looked at the manual (search for "parse tree" to find the spot)? It suggests putting node creation in an action with your left and right descendants being $1 and $3, or whatever they may be. In this case, yacc would be moving up the tree on your behalf rather than your doing it manually.