[antlr-interest] LPG WAS Retaining comments

[Olivier Lefevre]

Olivier Lefevre wrote:
> I still think it useful to think of the parse tree as something the tool will 
> build for you automatically (if you ask it to) whereas the AST is 
> something _you_ must build, making _all_ the decisions.

To elaborate just a tiny bit, you might say this is a superficial 
difference but if you ask a tree from the tool it will of necessity return 
a parse tree because that's the only thing it can return (it can't possibly 
know what kind of AST you want) whereas if you build the tree you will, 
well, not "of necessity" but almost certainly build an AST of sorts, 
reflecting your post-processing needs and thus the semantics of the 
language. Thus in practice the parse tree vs. AST divide tends to overlap 
neatly with the by-default vs. explicitly built divide.

-- O.L.