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Hi, I'm Peter Chapman, and welcome to the first Office Hours

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for CS 262 Building a Web Browser.

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I'm your assistant instructor, and I'm filling in for Professor Westley Weimer,

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who's currently at a conference.

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My name's Andy.

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I'm the assistant instructor for CS 212,

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which is Peter Norvig's class on the design of computer programs.

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And I'm going to be filling in the role of the student today

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and asking Peter here

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all of the questions that you came up with in the forums.

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So let's start off.

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The first question we had, Peter, was why are we learning regular expressions at all?

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Why is this useful for a class on programming languages?

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The class is structured around building a web browser,

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and our web browser needs to interpret html.

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The first step to do that is to identify the parts of html.

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We want to identify which part is the beginning of a tag,

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the end of a tag, what's a hyperlink, what's just text and words and whatnot.

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We want to do that very concisely

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with the powerful tool that is regular expressions.

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Regular expression just allows you to write some text,

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and it very precisely and easily identifies

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strings that can match, say, our tags or hyperlinks.

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Okay, and I've seen the beginning of Unit 2,

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and it seems like that gets reintroduced then.

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Yeah, we use it a lot throughout the course.