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>> SPEAKER 1: Suppose now that I wanted
to give Scratch the ability

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to sneeze as well.

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Well, my first instincts would
be, as before, to make a

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block, call this sneeze.

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Specify that I'd like to specify
with a number how many times

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Scratch should sneeze.

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Thereafter clicking OK.

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Let me move this over to the right
to give myself some more room.

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>> And then let me again go to Repeat,
overriding the default 10 with n.

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Let me go to the say statement
and say not "hello", but

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"achoo" for one second.

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Then take a moment's respite.

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And that's it.

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>> Now I have a block called sneeze,
as well as a block called cough.

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So that now if I want Scratch to cough
and sneeze, I can simply specify a

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sneeze below his cough.

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Three times, say.

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Click the green flag, and I should
see indeed, cough, cough, cough.

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Followed by achoo, achoo, achoo.

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My most realistic sneezes to date.

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>> Now notice something that's
bad about this design.

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Even though I didn't outright duplicate
any puzzle pieces, I

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definitely dragged and dropped pretty
much the same puzzle pieces, giving

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the one function an ever so slightly
different name than the other, sneeze

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versus cough.

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So this is an opportunity for factoring
out some common code.

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Indeed, notice the only difference
between cough and sneeze is that one

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has Scratch saying "cough," the
other of which saying "achoo."

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>> So couldn't we somehow generalize this
code in such a way that we simply

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specify what word we want
to Scratch to stay?

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And depending on that word, it will
effectively be a cough or

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it will be a sneeze.

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So let's go ahead and do this.

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Let's make a third function and call
this one, "say." and I want it to

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accept, not just a number, but this time
a string, otherwise known as a

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word or phrase.

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>> And we'll call this "word."

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And how many times do I
want to say this word?

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Well let's specify a number,
calling it again n.

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And just to make this block more
readable, let me go ahead and add a

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label called "times." So that when you
read this block from left to right, it

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literally says "say word n times."

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>> Now let me go ahead and click OK.

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And now let me implement this block,
again using a repeat block.

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Specifying that I want
it to repeat n times.

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Specifying that I want to say
something for one second.

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But rather than something hard coded
into this function, let's instead drag

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and drop the word that's
been passed in.

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Let's then wait for one second.

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So now let me go back and refine my
implementations of cough and sneeze,

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in such a way that those two functions
call this third function, thereby

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minimizing the amount
of duplicate code.

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So let's literally throw
this code away.

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Let's throw this code away.

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And this time, let's simply specify that
cough should be implemented by

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saying "cough" some number n of times.

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>> And similarly, can we go back and
re-implement sneeze so that it uses

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say with an argument
of "achoo" n times.

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So what have we done?

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We've recognized the code that was
common to both our cough and our

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sneeze functions, factored it out into
a new third function, and then

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rewritten cough and sneeze in such
a way that they call that

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third and new function.

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>> Now we have absolutely made this whole
program more complicated than it

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really needs to be.

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After all, at the end of the day, we
just need Scratch to cough three times

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and sneeze three times.

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And we could have done that with
just a few puzzle pieces.

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But as our programs get much more
complicated, and our programs more

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sophisticated, this technique of
factoring out common code, or

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hierarchical decomposing your program
into smaller function, each of which

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call other functions, is a very
compelling technique.

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Because it will ensure that your code,
even as it gets more complex, remains

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easy to update and also very readable.

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>> Indeed, consider the end result.

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When the green flag is clicked, cough
three times, sneeze three times.

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And that's it.

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In fact, let's do exactly that.

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Click the green flag and we get one
cough, two coughs, three coughs.

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Followed by, we hope, once sneeze,
two sneezes, and a third sneeze.

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Hope he gets better soon.

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