Now for a quick quiz.

NULL string value supplied.

Well, because, sentences are more interesting.

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

The second function we are going to write creates a risk of all the prefixes for a given string.

Now, what is William's age today?

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

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.

This is not true. Let's take a look at the plus operator.

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

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

And then we have the resulting.

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

Parentral on the other hand, is shown over here.

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

That line above it is the context.

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

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

Y has the value of 2.

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.

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

It's a set of sets of strings.

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

It depends on the context.

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

The real trick is basically that you have done it.

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.

First we identify. Blue words and then afterwards we do the green words and we just feed in the string that we passed into the function.

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

Because a valid conclusion so once again, here they're giving us a statement and they want us to come to some conclusion.

Now, of course, I'm going to have to give you some data to make this make sense.

When you spoke about your aneurysm on TV, you gave a lot of people hope.

We're going to calculate the probability of the string woe is me, and we're going to calculate that beginning at the beginning of the sentence, which we'll mark with this dot character, given that we are starting at the beginning of the sentence.

Welcome to the Homework 2 solutions.

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.

Coronary vessels So, coronary artery and vein.

They may get a little bit bigger, but it will totally work.

In this problem we've been asked to define a function, cfgempty, which takes in a representation of a context free grammar, a starting state, and a list of visited states and determines whether or not that context free grammar is empty.

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

If you keep on following data dependencies and control dependencies starting from a given statement, the set of statements that you get, that is, the set of statements that could have possibly influenced the statement in question, is also called a program slice, also called backward slice starting from statement, contains all of the statements that the statement S in question would transitively depend upon.

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.

Shortly after I performed the first liver transplant,

Abby's and Ben's earnings given only this first constraint.

like HTML or SQL, the language of database queries.

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