Which of these give strings could be derived from P in this grammar.

Finally, here we have regular expression disjunction or choice either a or b that's easy to write with two separate grammar rules.

Then with the second one, we learn how to take notes and how to make sure that we can take notes in a way that we can replicate those sounds and structures later.

But let's take a step back.

For now, context free just means that if you have a rule

We've seen that before with expression goes to expression plus expression.

Here's one now.

All right. The question was which of these five strings are in the language of this grammar.

Grammar

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Use filter 'exclude. rsync filter 'filter rule

It's like trying to learn the rules of English grammar by reading a bunch of high school student essays and looking at what they get right and get wrong in common.

We call them terminals.

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

When I'm starting from exp, I can use any of these 3 rules, so in particular I could use the third one and just replace exp with number, so number is definitely in the language of the grammar.

An interesting note that I didn't cover in this course, but that's nonetheless true, is that the particular parsing algorithm that we covered also runs in linear time, is very fast for the same small class of grammars LRK grammars they're called that are accepted by these faster tools.

This sentence is grammatically correct.

Your eyebrows angle, or your neck moving, your whole body matters. it's not just gestures.

Here's a new quiz. The Great Grammar Fix Up.

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

That's one of the ways that you get towards true complexity.

In this multiple, multiple choice quiz,

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The sentence is not grammatically accurate.

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

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

And later on when I do solve this problem, I'm going to refer to this derivation in the form of a list where I took rules 0, 2, and 5 to get ab.

It's your punctuation and grammar.

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

Unsurprisingly, the input will be (a b b c).

The sentence is free from grammatical mistakes.

The real challenge then, is to try to figure out how we can change rules.

Here I've written down four claims.

We know the rules!

We're doing all of this because we want to master parsing.

Often, we think of the function as return in just one value.

The real devil is in the details.

For this reason, the Ministry has seen fit to impose a new rule.

So now it's time to make sure that you're following along with a quiz.

This might seem a little counterintuitive but remember the glory of parsing, or the glory of context free grammars, is that a very concise grammar notation stands for an infinite number of strings.

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

This is one of those things I show to my students because it's a complete bastardization a denial of any rules of perspective.

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

I could also have picked rule 2 followed by rule 3, and then eventually this will boil down to ei plus i.

I can get that by looping around the first rule twice and then ei.