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While Loops
8:15While loops are a pre-check loop construct that will run every time the expression is evaluated to true.
[MUSIC]
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We're gonna talk about loops today and
I tried to be funny and made it called,
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Feeling Loopy.
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Let's talk about some ground rules too for
this.
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This is a little bit different
than what we're used to.
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We've probably been working,
you can kind of kind of stop and pause and
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that sort of thing.
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We can't do that here, so I, also,
as Dave was talking about there,
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the amazing video editors
when we make mistakes.
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You don't see them unless
we include them on purpose.
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So I might make a mistake while
I'm up here, but what I want to do
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is I want to talk about failure
a little bit just before we start here.
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I want to encourage you to
view failure as a good thing.
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Okay?
Because, and follow me,
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hold on a second, I know you're like,
no, it doesn't feel good when I fail.
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You were trying,
you were trying something.
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Right?
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And trying is learning.
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Okay?
So, you're gonna get there.
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You get there through failing.
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So, in this environment,
if anybody fails, if you go like this,
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it's the fail wave, and you can clap.
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I want everybody to clap crazy,
if I fail, I'm gonna raise my hands, and
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I'm gonna expect you to clap for me.
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So, good?
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Here's an example.
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When I film Java basics,
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we always try to cut, we try to make
these videos 10 minutes long, right?
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Because that's what
you're attention span is.
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We try to keep everything
at about 10 minutes,
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maybe a little bit less than that.
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And so
we try to cut things a little bit short.
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And so I cut the portion of my class on
loops, I cut it pretty tight and I failed.
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So, sorry.
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>> [APPLAUSE]
>> But I'm gonna try today to fix that.
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So let's fix that.
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Let's go and we'll dive a little
bit deeper into that stuff.
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Another thing that's on
the negative side of things.
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Sometimes when we say, are there any
questions and people have questions, but
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they don't ask questions.
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Let's not do that, okay.
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So if you have a question somebody
else is thinking about that question.
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Somebody else, you're not the only one.
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You're like,
oh he didn't explain that very well.
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I wanna know about that, but
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I don't wanna say anything cuz I
don't wanna look like I'm failing.
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No, if you have a question,
I'm gonna stop.
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That's how we're gonna do
this ten minute thing.
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This is the ground rules.
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We're gonna stop, maybe a little
bit shorter than 10 minutes.
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But we are going to stop each time,
and I'm gonna ask for questions and
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I am going to clap.
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I am going to have people clap for
you if you ask the question.
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Okay?
And we will feel good.
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Okay.
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So here we go, actually, while there are
questions, I will continue answering them.
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Right, it's like the loop, right?
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So, a loop, okay, so
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there's like a sequence of instructions
that you want to happen again and
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again, and you want to continually repeat
them until a certain condition is reached.
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Until something that you've said stop.
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Stop doing that.
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Keep doing these things and
then stop at this certain time.
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And there is different ways
of doing them in Java.
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So let's look at a couple of them.
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While loops is what we're
gonna start with here.
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These are commonly used
when you don't know how
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many times you're gonna
loop through something.
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There's some sort of condition that
you're going to eventually hit, but
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you don't know at the start of it.
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You don't know how long
that's going to be.
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Right?
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Now, Java has a pretty cool feature that
allows you to check stuff before hand,
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or if you want to, you can do it
afterwards and that's the pre-check.
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And the post-check.
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So there's two different types of loops.
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There's a while loop and
there's a do while loop.
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So let's take a look first at the while
loop, and that's a pre-check.
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That's the pre-check version.
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The cool thing about that is it's
sort of got a built in if, right?
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All right, so what happens is,
if you hit a while loop and
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the condition isn't there, you're
never gonna run the code inside of it.
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So let's take a look at some
pseudo-code really quick.
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So this is pseudo-code,
I am not very good at writing pseudo-code,
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it usually ends up looking
a lot like Python.
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But I don't want it to look like Java.
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I just want you to think through
this a little bit first.
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So here's an example of a while loop.
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So we'd say, hey, are there any questions?
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And while there were questions,
if there were any questions.
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If there weren't any questions I
wouldn't have a question to answer.
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While there's questions,
we'll answer the question.
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And then I'll say,
are there any more questions?
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And we'll just keep on going,
keep on asking.
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Once there aren't any more questions,
we stop, we pop out, and
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we go to the next slide.
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Make sense?
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All right, I'm gonna do a live
coding example in workspaces, so
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it's on the Internet.
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And that's breaking two rules,
you don't live code and
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you don't use the Internet
during a presentation.
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So, get ready for the fail whale.
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Okay.
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That worked, the Internet's working.
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I have the weirdest project that I have
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ever created in my life
on this side over here.
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These are what we're gonna walk through.
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So the first one that we're
gonna look at here is questions
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I've built the shell that you're all
starting to get familiar with I'm sure.
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So we've got the start of a program and
we have a console available to us.
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Don't need to worry about that.
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So we want to ask,
were there any questions?
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So we'll make this pretty basic.
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We'll do a console, and we'll do
a read line and we'll say are there
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any questions?
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That's gonna store whatever they entered
into this variable any questions,
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which is a string.
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We're cheating a little bit here,
but, hey, it's a demo.
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So, while anyQuestions=yes, and
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it's only lowercase yes
that's going to accept.
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I'm aware of that bug
that I just introduced.
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Let's make this app,
let's do like version one of Siri.
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That sound good?
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We'll do Siri on the iPhone, you ask her
a question and she tells you what happens.
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So this is what happens when I ask,
I say Siri a question.
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We'll say what is your question?
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Okay, so
Siri is going to respond with, I don't
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know if she says this to you, but
she says, I do not understand.
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So again, that's the printout.
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We're formatting and then we're going
to stick in the question she just said,
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because that's exactly what
she says to me every time.
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To know what you mean by hope.
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What do you mean by call mom.
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So okay any questions?
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Now this is the variable that we set
above outside of the scope right.
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We set it here to this, but we're going
to say are there any more questions?
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Okay.
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So, we're inside the while loop.
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So here's the while has these breaks here,
and see how it's highlighting in yellow?
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The coding here is going to loop each
time as long as things equal yes.
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And then of course we're going to pretend
that we're going to go to the next line.
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Okay?
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All right, and then I am going to use
the mail line here to compile our program.
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So we're gonna compile questions,
and then we're gonna run it.
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Then we're gonna see how it works.
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What do you think?
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Think we did it, or
think we're gonna get a fail wave?
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Let's see.
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Oh!
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>> [APPLAUSE]
>> Thank you.
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What did I forget?
I forgot to close that method out.
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I do that all the time.
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Do that all time and the video guys
get it all the time, cleared up.
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All right, so let's clear that up.
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Here we go.
All right, are there any questions?
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Actually, that's actually the next slide.
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The next slide is are there
any more questions?
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Are there questions?
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Remember, it's a good time.
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Anybody that-
>> This is actually [INAUDIBLE].
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>> Okay.
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>> But how did you get into [INAUDIBLE]?
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>> [LAUGH] [APPLAUSE]
>> Christine, do you wanna answer?
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>> [INAUDIBLE]
>> Woo!
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>> Awesome.
[APPLAUSE]
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>> [APPLAUSE]
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>> Think how happy that makes me.
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That's awesome.
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So are there, there was a question.
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Let's see it, see what Siri has to say.
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>> [LAUGH]
>> [LAUGH]
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>> Siri doesn't understand,
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she doesn't know.
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Oh, and I forgot.
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She asked, but I didn't put a new line,
so I also fail there.
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[SOUND] Shoot.
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But anyway, so there should be a new line.
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Right, so it's that percent end.
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Cool.
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It's a feature.
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Is there another one?
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Yeah, it's asking again.
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Is there any more?
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Let's see, where's he at?
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I should've done the fail wave.
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Oh, next slide, cuz I hit the.
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Fail, totally fail.
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>> [APPLAUSE]
>> Thanks.
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