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

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

That line above it is the context.

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

Build the system so that anybody can contribute at any amount.

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

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.

A context free language is also a set of strings but can be represented by context free grammar, and what these 3 questions are asking us in this problem is to determine the relationship between a regular language and a context free language, so let's say this bubble represents the set of regular languages.

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

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

We'll talk about it in a lot of different contexts.

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

In theory, you could compose it over here as well.

It depends on the context.

Well, because, sentences are more interesting.

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

like HTML or SQL, the language of database queries.

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

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

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

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

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

Units 3 and 4 were relatively abstract to some degree, intentionally so.

Coronary vessels So, coronary artery and vein.

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.

It's going to turn out that the best known research idea for figuring out values as they flow through various functions in your program is related to context free grammars or, more formally, context free language reachability.

This branch of the family is all about representation.

This is always true because we have our Pac Man diagram here, and also because you can take any regular language and represent it with a context free grammar.

Here I've written down four claims.

These are both infinite, infinite grammars.

We often want to check and see if a string is in the language of a context free grammar or matches that context free grammar, can be derived or generated by that context free grammar these are all the same question and one way to do that was memoization, which for many years I always wanted to call memorization, but it's just not.

In most interpreters, this is a problem.

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

So, here you have a giant vein, this is a vein, and you have an artery.

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

These are just the ESPN SportsCenter version of the game.

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

The brain is recording all information and driving all change in temporal context.

That's an excellent question.

This New York means the same to me as it does to everyone else.

In particular, it's a set of strings that can be represented by a finite state machine or a regular expression.

A can be replaces by B in your grammar and you have an A, you can replace it with a B regardless of what this nearby context is as long as you hold the context the same.

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

unparsed entity reference in wrong context

It's a set of sets of strings.