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-Hi.

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In the redo of the third week,
so right now,

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we will look at how we can handle
an expression to represent dice.

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For example,

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imagine that we would like
to know the result of an expression

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being "2 D20 + 1 D4".

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This expression is what you might
encounter in a role-playing game

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such as "Dungeons and Dragons"
for example,

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where this would mean

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"give me the result of a roll
of two dice with 20 faces

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plus the result
of one dice with four faces."

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In order to make everything work,

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we will need a class to represent a die,
a class to represent dice handle,

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and we will look
at how we might implement it.

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Let's go over to our System Browser.

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We will create a die class
that is a subclass of Object.

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We will give it an instance variable
to be the number of faces,

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and we will put everything
in the "Dice" package.

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Let's save this, Cmd+S.

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We will filter out
all the other packages

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and we will write an initialize method.

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When you write an initialize method,

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it is good practice

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to always check for the initialization
of the superclasses.

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We will write "super initialize".

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Then, we will set
for the number of faces to be six

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so we will have by default
a dice with six faces.

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Let's save this.

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And what we will do
is instantly test this behavior.

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Go over to your Class,

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we are going to write "DieTest",

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to be a subclass of "TestCase",

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we do not need this anymore,
and save everything.

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OK, we have our "DieTest", we will write

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our "testInitializationIsOk".

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So, what do we need to test?

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We need to create dice,
so "d = Die new"

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and we would like to check

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that the number of faces of d
is actually equal to 6.

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"Faces" is in red
because we have not defined it

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but as we saw last week,

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this is fine, the debugger will handle it
so let's just save it

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and then, run the test.

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"Faces" has not been understood,
that is fine

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because we will just create it right now.

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Create in the Class Die

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under the "accessing" protocol. OK.

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This is exactly what we want,
the default behavior of the getter.

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Let's press "Proceed".

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Our test passed,
so we can just click there

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and now it is refreshed.

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Our test passed.

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So, right now, what we can write
and what we will need

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is a way to roll our dice.

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Let's go over there
and write a "roll" method.

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What we will use

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is "faces atRandom".

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Basically, we would like to get a result
from 1 to the number of faces.

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Let's look into the Playground.

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If I write 6 atRandom,

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double-click, Cmd+P,

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you can see that it output
a result from 1 to 6.

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This is exactly the behavior
we would like to use for our dice.

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This is our roll function
that we will save by pressing Cmd+S.

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We will test it right away,

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so "testRolling".

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And what is good practice
for random behavior

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is to repeat the test
on the random result,

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so "timesRepeat:" is the way to go.

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This method is applied to a number

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and this means it will repeat 10 times
the thing we will get.

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What we will give to this method
is a code block,

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so basically,
it will be between brackets.

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We will write "self assert"

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and what we would like to assert
is basically

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that the roll of a dice
is between 1 and 6.

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This means it will check
for the result of a dice

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to be between 1 and 6 with the "assert"

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and it will repeat this check 10 times

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so let's save it, run it,

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and if you are not confident

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in the number of times
you tested your random behavior,

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you might increment it up to 100
for example, save it, run it.

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Everything is running,
we have a good start,

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it is a good time to save our repository.

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Let's go over to Iceberg.

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Let's go to Add,
we will save the project under "Dice".

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OK.

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Double-click on the project,

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our project "Dice".

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We will add our Dice package.

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Add.

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It says that we have uncommitted changes

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so let's commit right away.

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"Initial commit", what did we do?

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We created "Dice initialization

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and rolling with tests".

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Perfect, press "Commit".

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This is our GitHub properties,
so "QDucasse"

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and your email address.

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Cool.

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Everything is saved now.

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We can just keep it here.

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Keep this one as well,

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and we will write another test
and the associated method.

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For example,

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one thing we will need if we need
a die with 20 faces or with 4 faces

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is a way to specify the number of faces,

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for example we will write
something called:

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"CreationIsOk".

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And remove this.

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I would like to have a method that
I can call like this: "withFaces: 20"

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and I would like to assert

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that my number of faces is equal to 20.

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How do I handle this?

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You can see it is written in red
but as we saw last week,

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we will let the debugger handle it
so press Cmd+S.

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Run it.

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The method "withFaces"
has not been understood

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so let's press "Create".

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We will define "withFaces"
in the die Class.

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"Die Class",
under the instance creation protocol.

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OK.

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This time,
it does know how to handle it

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so we will write for it:

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"d"...

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"d" will be our new dice
and I would like it

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to have the number we provided
as faces,

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"d faces",

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and just give us d.

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Cmd+S.

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We will proceed.

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"Faces:" has not been understood.

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This is because we have not defined
the setter.

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So, let's create it in Die

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under the accessing protocol.

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OK.

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This time, it recognize it

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so "faces : = anInteger",
that is perfect.

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Let's proceed.

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It is red,

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but if we click on it again,
it is green, so that is perfect.

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You can see that now we have three tests,

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we have the basic functionalities
of our Dice running, up and ready,

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so it is a good time to save everything
on our repository,

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so it is there or we can see it there.

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Let's just commit

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and we will write:

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"Class method to specify
the number of faces with test."

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Cool.

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"Commit".

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Right now, we have
all the basic functionalities of our die

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and we will see in the next part
how we can handle a dice handle

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and how we can handle
multiple dice together.