OK, so the goal at hand is here, I
have two glasses of colored water.
So we have some purple here.
[WATER POURING]
OK.
And we've got some green here.
[WATER POURING]
And the only goal at hand is
to do a very simple operation
like we needed to do
quite a bit last week,
which is to swap two variables
just like we swap two numbers.
So if you could go ahead and
get the purple liquid in here
and the green liquid in here, go.
[CHUCKLE]
FARRAH: Is it OK if they overlap?
DAVID J. MALAN: Ideally, no.
We want to put only purple
here, and only green here,
and no temporary store.
[LAUGHTER]
FARRAH: Oh.
DAVID J. MALAN: OK,
but you're hesitating.
Why?
FARRAH: Because you told me they
couldn't touch [CHUCKLE] and--
DAVID J. MALAN: Well, you
can touch the glasses.
But you're hesitating to swap them, why?
[CLINK]
OK, that's just cheating.
[LAUGHTER]
[APPLAUSE]
[CHEERS]
OK, very clever.
Supposing you can't
just move things around
in memory, what if I gave
you a temporary variable.
FARRAH: OK.
DAVID J. MALAN: Does this help?
FARRAH: Yes.
DAVID J. MALAN: So how can we now get
purple in there and green in there?
[CHUCKLE]
FARRAH: Can I put purple in here first?
DAVID J. MALAN: Sure.
FARRAH: I'm going to spill it.
DAVID J. MALAN: It's OK.
[WATER POURING]
OK.
So purple goes into the
temporary, very nice.
[APPLAUSE]
FARRAH: Thank you.
DAVID J. MALAN: Green
goes into what was purple.
FARRAH: Yes
DAVID J. MALAN: OK, good.
And then purple goes in--
from the temporary variable
into the original green glass.
Now, a proper round of
applause if we could.
OK.
[APPLAUSE]
Thank you.
FARRAH: Thank you.
