End Color

And your typical context free grammar is just a set of rewrite rules with a nonterminal symbol on the left, an arrow, and then some terminals and nonterminals on the right.

Kitt, shut down the computer now.

Shutting down all systems.

It can be 1 non terminal like here.

Finished testing your system...

unexpected end

What's special about the terminals is they never appear on the left side of a rule.

I'm going to be as generic as I can to handle all the possibilities.

A derivation just means starting from some non terminal, follow the rules to derive a sequence of terminals.

A could be empty. B could be empty. Pqr could be empty.

Unexpected end of input

That's going to be true or false.

What I've done here is what's called a derivation.

So let's say we haven't seen any of the input yet.

At the end of Breckenridge Road.

The option to override detonation procedure has now expired.

The end of the list of matches has been reached

In a plot behind my old place over on Breckenridge.

I'm going to pick the first one. We'll replace noun with the terminal I.

We're just going to return the terminal because that's an example where if you start from a terminal you get a terminal.

Sentence can be replaced with subject followed by verb followed by object.

(a, bb, c).

Here I've recopied the grammar.

Soon as they open that door, it's all over.

And we keep on doing that, slice after slice.

Let's say that we've got x goes to ab dot cd coming from position j in chart i.

We've already seen 2 possible ways to do it.

The replacement can be anything.

Here is our tree, and at various places although it's starting with the trunk or the root it branches out, and all of these intermediate parts in the tree represent none terminals in the grammar.

You reached the end of the list of matching items.

INT reduces to, or can be rewritten from, E using one of the rules in our grammar.

These are always going to be terminals.

To meet her new beloved anywhere But passion lends them power, time means, to meet,

We still have object.

In order for the grammar to make a string, we have to be able to replace all of the non terminals with terminals.

Sometimes the leaves are called leaf nodes, which is a bit ambiguous.

There are really four parts of our parsing state the left hand side nonterminal, some list of terminals and nonterminals before the dot, some list after, and j.

And I've drawn (a) and (b) and (c) and (d) in purple because we're not sure if they're terminals or nonterminals.

Just an open parenthesis.

So that's what we're going to include there, and then we're going to close our div, and we're going to end our loop.

Remember that we're encoding parse states as simple tuples.

Once you get there, you're stuck, and the process terminates.

Expression can also go to expression minus expression or expression in parentheses, or just number, and here I'm writing all of my terminals and non terminals as strings just to make equality checking easier.

Otherwise, it's going to be false.