Re: understanding the intuition behind LL(k) parsers and LR(k) parsers

On Fri, 2006-04-21 at 23:47 -0400, Mark F. wrote:


> .... A bottom up parser has to start with some kind of "last
> terminal" then build the tree in upward direction. Intuitively where
> would the bottom-up parser start if presented an input file. How
> does it find this starting point, of the parse. It has to be the
> deepest part of the tree. But how do you detect this, without
> expending the tree first from top-bottom? Is my thinking faulted?


> [Bottom up parsers use a state machine, like the one in a DFA regular
> expression matcher. The states implicitly encode all of the possible
> matches, and when the parser gets to a state where there's one complete
> match, you reduce the rule. -John]


For notes on a particular implementation of a bottom up tree builder,
check out the JJTree documentation:


https://javacc.dev.java.net/doc/JJTree.html


It talks about ways to customize the node tree as it's constructed; lots
of good stuff there.


Yours,


tom

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