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welcome to this jam session

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and then this jam session I'm going to
show you

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how the principles functional
programming that we've seen

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in the course for Haskell can be applied

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a.m. to their language cop Gotland

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is a language designed to buy JetBrains

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and if you're in and ellijay user like I
am

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and you can and download the plugin for
cropland

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and and play with a child let's go and
messy

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how we can do functional programming in

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a a normal language an

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here is the Anna and main

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function for our call in program just
like

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job on sharper than made

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takes array of strings as an argument
and

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inside the body we see a couple of
expressions here

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and I want to walk you through them and
and show you

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how this relates today and Haskell code

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that we have seen and notes that for me

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functional programming does not imply

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and not using side effects functional
programming does not mean

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using pattern matching for me functional
programming means

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using higher-order functions whether
they're you're not

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an and focusing on expressions

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various statements and got then you can
define you to both they're both so I can

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define

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var and why and

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initialized tu wong and then I can say
why

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and plus equals Wong

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and this just work and I have no problem
at all with that

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okay but what I wanted to show here

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is and the functional programming
features

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that are supported by cop so let's look
at this for statement here so I define

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a an immutable variable here are the

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just a name a square and that goals

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the an function foo and Fu is defiant

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here as a function you see the and

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if I over over this it and that may be a
little bit

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small to see I'm on the screen but and
got then has type inference for the

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return type show here

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it said Tekken that's very small yellow
thing that you

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currency that the type of

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through and is a function that they can

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and & Returns & and here I

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call through a forty-two and I printed
now another thing that we've seen in

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Haskell

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and the less comprehension ce work these
range expressions where we

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we could ride in Haskell square brackets
Wong dot dot

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am an got and support something very
similar so I can say for action

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at the range 125 print X

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so here you see that this shame gonna
syntax and I the years

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range comprehension appear

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in and other languages as well now

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the next example shows

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am some higher order functions and the
syntax that got land uses for them to

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hear

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I declare lest a list of the values 1234

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and then I mapped the function a

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I rode along that expression a a row
eight times to over it

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and then I filter out all the values

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less than five and you see that there's
two ways to define

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along the expression the first one here
is where you name the

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arguments and arrow and then the
expression body

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and the longer is enclosed in curly
braces

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you can leave out the

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an Iran's around the map

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but I can have liked that to put them
there

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explicitly and hear the filter is seeded
if

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a long the expression just takes one
argument we don't have to name it

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and we just call it it's very similar to

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when you have an object that the and
implicit

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context that this parameter is called
this

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when you have a function with one
parameter

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it make sense to call that one parameter
give it a special name

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such that you have to write less

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okay sure you can do everything that you
learned in the course

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with with maps filter fault an

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you can do in Cortland as well and

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is he here there's I'll all the
functions

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defined on lists that you will recognize

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from the Haskell brilliant most
programming languages if you look at the

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API

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for collections they are very familiar
and they all contain

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and the same Iran function sometimes

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names are slightly different different
but in general

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and that you'd be very familiar

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one nice thing and that got land has

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and which C sharp also has our extension
that its

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so in this case I define an extension
that at some

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on integer let's look at and the
definition for

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the some extension at issue here you see
and defining

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and a love the expression

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and this into dots their

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indicates that some as an extension
method

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on ent and it takes parameter logical
that other

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and its returns and ensure here you see
and the

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type and then the body of the

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I'm extension method just at this

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to other show in this case decision
scope

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and an ranges over

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the an receiver and I think this is also

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and quite nice its less for boast and
the way you define extension medicine C

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sharp

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very deftly finest static mat did you
have to explicitly name the parameter

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dish modifier in front and this is

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very very concise and then we can just
call

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Wong dot sum of two

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and lectures and when we talked about

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a defining data types I compared

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haskell at algebra datatypes with
glasses

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in object-oriented languages and

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is word emphasizing that if you look

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at the course bonuses if you look at
while the similar

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haskell als right data type is really

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kinda streamlined way to ride

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a class hierarchy and with constructors
and strong

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and better matching is really a
streamlined way to do is check

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let's see how we would be fine the type
of lists

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in got lawn and how we can t find

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one of the standard triggers it
functions over lists

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as an extension that'd using better
matching

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or and est and then you will see

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that there's a little bit more syntax
then in Haskell or maybe even the same

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amount of characters

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an but the important thing here is that
you can take the concepts from Haskell

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algebra dated ives and apply them in an
object or language

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and vice versa if you have inheritance
hierarchy

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in an object turned language you can
often mobile that also

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using haskell algebra datatypes

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here's a.m. the type

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a blessed so what I do is I D find

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abstract class list and this data
modifier

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is a special modifier an that you can
put

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on the government class that well and

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make sure that a bunch of things are
implemented like equals hashCode and so

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on

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and you know that's rather easy

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and then I'd be fine to derived class
issue in Haskell these would be on the

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right hand side of the algebraic
datatype Chanel

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is a special case of alleged and college

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is a special occasion the list that as a
hat

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of type T and a tail of typed list of
tea

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again as you can see if you squint to
read or you put on some different

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colored glasses

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this glass decoration is

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isomorphic to the Haskell definition for
this

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one important difference of course is
that and

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what then is a strict language so these
are not lazy so if you want to do lazy

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list

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we have to do a little bit more work and
I we have to make sure that

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an detail remains and evaluated and one
way to do that

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is by creating a thank for that but
thats

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topic for a different time now let's
look at how we define

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and function recursively over

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this new list type an so here we define
length

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and length is defined as an extension
method over Leicester you see that

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list here has no Matt dense

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am but I just define them outside

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and here's my better match and I check
when this is nel

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the result is 0 and I should lined it up
properly

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so when adl the lest nil

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lactis 0 that's exactly like

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and has gone and when we have a college

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an what i do is it the result is one
plus

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the length of the day love the list and
so instead of

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better matching to get at detailed the
list

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I am calling here the access your

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to get detail and since a goblin
compiler

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and cannot determined that I'm not

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and extending this at data class anymore

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I have to put here this purist als loss
an

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to draw an exception but we know that
this will never happen

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but if if we do this if we don't do this
and

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we will get an error here and say that
arnelle's

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clause is required okay and then we can

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and create a less DEC looks very similar
to Haskell views named arguments here

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and recreate the list and that just
contains the value 3

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and then we calculate is like so let's
run this code

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and to see if everything I told you

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is actually through an

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their Eagar

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through on it area so and

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going from top to bottom this wrong here

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is the length of and this last

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well that national days only develop you
three so

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their ego if I compute one place to

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history and if I take the numbers 1 to 4

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and I'm am double down and then filter
out the ones that are less than five I

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get the list

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and 24 if I print numbers 125 I get the
numbers wrong 25

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and if I square 42 I get 764

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so there we go and programming got land

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if you want to learn more about got you
can go to the got their website

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am and you can jump and immediately

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using all the skills you learned and
haskell

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part of this lecture thank you very much
and see you next time