That's much more important than knowing the particular syntax for any language.

Finite State Machines, adding a lexer that follows them automatically,

Look at these two intersecting lines.

You might think, Boy, is there a context expensive grammar out there? What's the opposite of free?

It turns out that interprocedural data flow analysis is the same problem as, in a theoretical sense, context free language reachability, which is the same problem as could I generate a string in a context free grammar.

These grammars that we've been introducing describe something new context free languages.

unparsed entity reference in wrong context

It relates grammars to parsing, which is one of the concepts in this class.

All right. Now that you've gone to the hard work of defining all of those procedures,

They specify sets of strings, and they can be implemented under the hood with finite state machines.

It depends on the context.

This branch of the family is all about representation.

I am just gonna pause for a moment to let you think about that.

This concept is not particularly tricky, but it does require a context free grammar.

We need to know where we came from in order to know where we're going.

So in lecture, we spent a lot of time learning about context free grammars and languages.

like HTML or SQL, the language of database queries.

But that's an example of an application that also uses this sort of linguistic analysis perhaps a little less related to context free grammars but still in the same vein.

All of that is going to matter for figuring out the true interpretations of programs.

You might use the Let's Begin section to set context for interpreting the video or to define a learning objective for your students.

In fact, just as we saw that regular languages and regular expressions weren't powerful enough to do everything we needed they couldn't handle balanced parentheses, so we couldn't use them for parsing it's going to turn out that context free languages and context free grammars will only take us so far, and we're going to use additional techniques like interpretation or keeping track of local variables in order to find other things out.

Well, because, sentences are more interesting.

I can do that, just wait. (ding!)

I'm afraid of losing this place.

The set of languages that can be described by re write rules or grammers like this are called context free languages.

Here I've written down four claims.

Y has the value of 2.

But if right above it I've written X 0, then we'd get a different answer.

And that gives us the entire expression is 0.229.

It handles LL. It handles LR. It handles LALR.

That line above it is the context.

We're going to design together formal grammars that exactly capture HTML and JavaScript or at least interesting subsets of them.

This is called being lazy, and it's a phenomenal virtue when you're writing programs.

He couldn't understand the sentence.

Actually, they're both just concise notations for specifying possibly infinite sets of strings.

... the misspelled word shown in context...

To do this, we use 2 key techniques lexical analysis, which broke the string down into a stream of tokens, and syntactic analysis or parsing, which takes a string of tokens and checks to see if they adhere to, if they conform to a context free grammar.

All right. So, it's another one of these puzzle like questions.

They're the actual input that we're trying to match.

Sometimes this statement is true, and sometimes it's not.

A context free grammar can capture the language a N and b N, where N is the same.

I can't make out the meaning of this sentence.

We much prefer grammatical sentences.

If you want to go try Oink out later on, it accepts this same sort of context free grammar format that we're used to.

So we're going to need something more than just parsing, more than context free grammars, to reason about programs that include substrings like X 2.